Sticky problems with mapping historical New York City

Author’s time-lapse of Lower Manhattan’s street network development from 1609-2020

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With help from digital and spatial mapping software, urban historians and geographers are examining city growth over time. Time-lapse evolutions are proliferating online of street network development in cities like New York City, Barcelona, London, and Berlin.

In most time-lapse studies, geographers encounter problems with lack of data. The older the city, the less data there exists about pre-modern population densities, demographics, and street networks. This lack of data is a problem when mapping the geographies of older cities.

A way around this problem is to look at street network development as a proxy for population size. The more streets there are built, the more people this city should have, the logic follows. In theory, this seems to work because cities with larger populations require more streets and occupy more built-up area. Knowing how much surface area a city occupies, coupled with knowing the average size and number of occupants in a typical block or building, allows a simple calculation of total population (people/acre x surface area). In addition, more historical data exists about street networks (from maps) than exists about population and demographics (from the census).

The problem with this method of using streets as a proxy for demographics is that cities that occupy more surface area and with more streets do not necessarily have more people. There are several reasons for this:

  • Available land: Some cities are built in harder geographies where acquisition of new land for development is prohibitively difficult to acquire, such as Venice. Manhattan’s high density and land values descend, of course, from a demand for housing that far exceeds supply on an island bordered by water.

    For instance, Oklahoma City covers 621 square miles with a 2018 population of only 650,000. New York City covers 302.6 square miles (half the area of Oklahoma City) and has a 2018 population of 8.4 million (thirteen times the population of Oklahoma City). Despite the major differences between these two cities – in population and surface area – the sum total of all streets if they were lined up end to end to form a continuous road is about the same for both cities. Similarly, the Manhattan grid is identical with the same street widths and block sizes from end to end of the island, even though population density in buildings within this gird varies from zero people per acre to over 200 per acre. Flexible street networks support any variety of housing types and densities.

  • Zoning: Some municipalities are stricter than others in enforcing discrete and different land uses for residential, commercial, industrial, and mixed-use. The legal landscape of Manhattan has evolved significantly since the first zoning laws in 1916 restricted building height and density. Since then, city government has more clearly articulated rules about minimum apartment size, ventilation, fire escapes, and water supply. City government has also pulled industrial (and often more polluting) land uses away from residential areas in the name of safety and health.

    Although few of these legal and zoning changes are explicitly imprinted on the street network, they have a tangible and important impact on the quality of urban life. This zoning has largely resulted in lower population density because of restrictions on landlords cramming hundreds of people into the smallest space possible for the maximum profit. Now, over 40% of all buildings on Manhattan could not be built today for violating NYC’s zoning code for at least one reason. For instance, most buildings in neighborhoods like West Village and Lower East Side have not changed in a century; there is limited demolition and reconstruction every year. However, population density has significantly fallen as apartments grow larger and rooms formerly designed for multiple people in one room now only have one or two occupants. Even if the buildings and streets don’t change, the ways they are occupied can and do.

  • Transportation patterns: This is the biggest factor encouraging extensive and rapid street network development with low population density – i.e. sprawl. Before the nineteenth-century inventions of railways and streetcars, and the twentieth-century’s auto-based suburbanization, transportation and commuting were prohibitively difficult. People needed to live near to where they worked in what was largely a pedestrian and walking city on unpaved streets. Transportation challenges caused urban growth to be dense and built-up near to places of employment. As a result, many cities like Paris and London might appear small on maps and occupy only a few square miles pre-1800, even though their population and economic importance were far larger than their surface area on maps leads one to assume.

Before the introduction of subways in the early twentieth-century, this difficulty with traveling greater distances over land and water drove a uniquely dense form of New York City urbanism. Manhattan, by 1900, had over 2.3 million residents in comparison to only 1.6 million in 2020; these people were crowded into dense blocks with upward of half a million people per square mile. In decades following, although Manhattan has lost 700,000 people in ~100 years, the street network is today almost identical to a century ago – no smaller and no larger despite major shifts. These shifts in density and demographics simply do not show up on conventional street maps.

My animation below shows the evolution of Manhattan’s built-up area population density from 1800 to 2010. Notice the steady upward march of street development versus the sudden spike in population density on the Lower East Side in 1910 at over 300,000 people per square mile (in contrast to less than 90,000 in 2010). For every decade after the construction of subways allowing easy access to Manhattan jobs from the outer boroughs, the island’s population density has fallen. Notice how fluctuations in population density and total population on the island operate semi-independently of street-network growth.

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Modified from Shlomo Angel and Patrick Lamson-Hall’s NYU Stern Urbanization Project, here and here.

The animation on the left tells one story of continuous and upward development, while the animation on right tells a more nuanced story of population density. The challenge is to find a graphic representation that tells both stories, as neither captures all the nuances of urban history.

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Possible Solutions:

Discussing this problem of street networks with professor Kenneth Jackson, he suggested looking at building Floor Area Ratio (abbreviated FAR), which is the building height and size relative to the amount of land the building occupies. This method of representing urban growth would, in theory, produce three sets of maps: 1) a map of street network development; 2) a density map of people living per square mile; 3) a map of building height and size. This would complicate things but produce a far more accurate representation of urban growth – how to represent this and if the data exists is another matter.

These three factors – streets, FAR, and population density – act semi-independently of each other. Different urban typologies will share a different mixture of these three factors. Only through analysis of the relationship between these three factors can one begin to understand the underlying demographic, economic, zoning, and historical differences between neighborhoods. For instance:

  • Downtown commercial district like Lower Manhattan: low population density but high FAR. In this case, FAR operates in inverse proportion to residential population density. Buildings can be dozens of stories but have no residents.

  • Slum like South Bronx in the 1980s: extensive (though poorly-maintained) street network development, high density, but low FAR because slum dwellings are typically informal without the construction quality required to build high. Buildings might be fewer than six stories and without elevators, as in the Lower East Side, but can contain hundreds or thousands of residents over the tenement’s lifespan. In this case, FAR and population density do not have an immediately correlated relationship.

  • Suburb like Forest Hills, Queens: extensive (and well-maintained) street network development, low density, and low FAR. In wealthier suburbs, in particular, FAR is kept prohibitively low. Restrictions on minimum lot size required to build, minimum house size, and legal hurdles on subdividing larger lots into smaller ones all serve to enforce a certain quality and price of residential construction that often prices-out lower-income communities of color.

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Left: NYC population by day. Right: NYC population by night. The population doubles by day.

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Density maps above are one illustration of FAR and help flesh out some of the nuances of Manhattan’s historical growth. Areas with the highest FAR tend to be commercial areas with daytime office workers and commuters. The left map shows the daytime population density of the over two million commuters. The areas with highest worker density neatly map onto the same areas of Lower Manhattan and Midtown with skyscrapers clusters. The right map shows nighttime population density of residential areas, which also neatly map onto areas with generally lower FAR. Notice the gray-colored zones in Lower Manhattan and Midtown with an almost zero nighttime population density, incidentally the areas with highest daytime density and highest FAR.

In twenty-first-century New York City, it is quite easy to examine the relationship between these three factors – street network, population density, and FAR – as the datasets are readily available from NYC Open Data. Yet, this all becomes more difficult, perhaps prohibitively difficult, for historical mapping. Calculating FAR for historical Manhattan is certainly possible through scrutinizing digitized historical Sanborn fire insurance maps that go so far as to specify building footprint, materials, and height. At the moment, this data does not comprehensively exist for the entire city, as building footprints and FAR must be calculated through manually scanning, tracing, and inputting building footprints from the New York Public Library’s collection for thousands (even millions of buildings) over hundreds of years. However, as technology improves, it may be possible in a few decades through advances in machine learning to translate historical maps into geographic shapefiles. If historical maps could be scanned and immediately transformed from image files to geospatial data files, the possibilities of using historical mapping to inform research are endless, as well as thousands of hours of tedious work would be saved. If and when there is the data on historical FAR, it may be possible to create a new paradigm and understanding of urban history.

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New York City Population Density in 1900

Author’s illustration based on population per municipal ward from 1900 Federal census

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NYC Coronavirus Tour

This NYC tour follows the route of Kenneth T. Jackson’s night tour. As a Columbia University undergraduate, I joined Jackson’s 2016 night tour of NYC by bike, from Harlem, down the spine of Manhattan, and over the bridge to Brooklyn.

With a heavy heart, I gathered my courage on 30 March 2020 to revisit my beloved NYC, along this same route in the now sleeping city attacked by an invisible pathogen. The empty streets hit me with emotions in the misty and rainy weather – perhaps fitting for the poor spirits the city is in.

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The tour route is drawn below.  Click here to view this drawing in more detail.

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Audio Effects from Freesound:  Street AmbianceHighway AmbiancePassing CarSiren BlastShort SirenLong Siren

New York City Water Supply Animated History

New York City has some of the world’s cleanest drinking water. It is one of only a few American cities (and among those cities the largest) to supply completely unfiltered drinking water to nine million people. This system collects water from around 2,000 square miles of forest and farms in Upstate New York, transports this water in up to 125 miles of buried aqueducts, and delivers one billion gallons per day, enough to fill a cube ~300 feet to a side, or the volume of the Empire State Building. This is one of America’s largest and most ambitious infrastructure projects. It remains, however, largely invisible and taken for granted. When they drink a glass of water or wash their hands, few New Yorkers remind themselves of this marvel in civil engineering they benefit from.
This animated map illustrates the visual history of this important American infrastructure.

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Sound of water and ambient music from freesound.org

New York City is surrounded by saltwater and has few sources of natural freshwater. From the early days, settlers dug wells and used local streams. As the population grew, these sources became polluted. Water shortages allowed disease and fire to threaten the city’s future. In response, city leaders looked north, to the undeveloped forests and rivers of Upstate New York. This began the 200-year-long search for clean water for the growing city.

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Credits

Gergely Baics – advice on GIS skills and animating water history
Kenneth T. Jackson – infrastructure history
Juan F. Martinez and Wright Kennedy – data

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Interactive Map

I created this animation with information from New York City Open Data about the construction and location of water supply infrastructure. Aqueduct routes are traced from publicly-available satellite imagery and old maps in NYPL map archives. Thanks is also due to Juan F. Martinez, who created this visualization.
Explore water features in the interactive map below. Click color-coded features to reveal detail.
Watersheds   Subsurface Aqueducts   Surface Aqueducts   Water Distribution Tunnels   City Limits

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▼ For map legend, press arrow key below.

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Sources

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For such an important and public infrastructure, the data about this water supply, aqueduct routes, and pumping stations is kept surprisingly secret in a post 9/11 world. However, the data presented here is extracted from publicly-available sources online, and through analysis of visible infrastructure features on satellite imagery when actual vector file data or raster maps are unavailable from NYC government.
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Contemporary Maps
NYC System and Shapefiles – Juan F. Martinez
Watershed Recreation Areas – NYC Department of Environment Protection (DEP)
General System Map – NY State Department of Environmental Conservation (DEC)
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Historic Maps
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Texts
Water Supply Fast Facts – NY State DEC
Encyclopedia of the City of New York – Kenneth T. Jackson
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Animation music – Freesound
Audio narration – Myles Zhang

New York City in a Box

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This pop up model in a recycled metal box (measuring 8 inches wide by 15.5 long and 2.5 deep) reveals a miniature world of New York City architecture and landmarks when opened. About 30 buildings made from hand cut paper and tin are spread across a flat ground of painted streets. Each building is made from a single sheet of paper that is cut and folded like origami to create different shapes and sizes. A hand cranked lever operates a hidden mechanism of chains and gears hidden beneath. These gears move the magnetized trains and airplanes through the city. The video below shows this mechanism exposed.

Click here to read an article featuring this project.

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Hand-crank and music box recording courtesy of Freesound.

New York City Subway Ridership

Could the movement of people in the New York City subway system be visualized as rhythmic breathing?
Linguistically, we often describe cities in relation to the human body. Major roads are described as “arteries” in reference to blood flow. The sewers are the city’s “bowels.” Central Park is the “city’s lungs.” At various times in history, key industries like textiles or finance, were described as the “backbone” of this city’s economy. Although cities are complex organisms. wordplay makes the giant metropolis somehow more human and familiar.
The 424 subway stations and 665 miles of track are analogous to the human circulatory system. Every weekday, the subway carries 5.4 million people, mostly to and from work (c.2018).  This movement during the daily commute is highly ordered, structured, and rhythmic – as Manhattan’s population swells during the daily commute and then contracts by night. Each passenger symbolizes the movement of a single blood cell, operating as one cellular unit in a complex system. With each paycheck, the oxygen of capitalism flows from the heart of Manhattan to the cellular homes in the outer boroughs.
Commuting patterns are analogous to the rhythmic expansion and contraction of the human body while breathing. By contrasting weekday and weekend ridership patterns, we detect the city’s respiratory system.

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sounds of breathingheartbeat, and subway are from freesound.org

In this animation based on subway ridership statistics by station:
● Dots are color-coded according to the subway lines they serve.
● White dots are for junctions between two or more lines of different color.
● Dot size corresponds to the number of riders entering each station within a 24-hour period.
● Larger dots are for busier stations. Smaller dots are for less busy stations.
Maybe the visual language of data can address this deeper need to humanize and soften the concrete jungle.

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Also published by the Gothamist on 22 January 2019.
If you like this, please see my animation of ridership patterns over 24 hours in the London Underground.

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Excavating Old Penn Station

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Through Penn Station one entered the city like a god. Perhaps it was really too much. One scuttles in now like a rat.

– Vincent Scully

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Bird’s Eye View from Northeast to Southwest in 1910-20

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Human beings, myself included, have an unfortunate tendency to appreciate people and things only after they are gone. Pennsylvania Station is the catalyst for the historic preservation movement.

– Kenneth Jackson

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The old Penn Station, completed 1910, had 21 tracks on 11 platforms. The new Penn Station has 21 tracks on 11 platforms. In the demolition process, not one track or platform moved. This similarity enables us to situate parts of the old structure in relation to the new. The photos below compare this structure past and present. The old photos are drawn from the digital archive of the New York Public Library, Historic American Buildings Survey, and Library of Congress. The current photos were all taken by Myles Zhang in March 2019. Current photos are as close as possible to the original camera angles. However, some changes in the station layout and access rights to the areas above make complete accuracy prohibitively difficult.

Curious how New York Penn Station influenced landmarks preservation? See this video from Khan Academy.

A 2015 article from the New York Times asks the question: What does architecture sound like? Considering this question, I thought to record the sights and sounds of the current Penn Station. So, the audio accompanying each frame in the video above is accurate to what the place sounds like from the location shown. The audio for the old Penn Station is my imaginative reconstruction of how the original station might have sounded like. Surely, the high stone walls, glass interiors, and electric trains beneath would have evoked a different aura and sound of luxurious rail travel. This sound track is copied from recordings and moving images made of NYC in 1911 and preserved at MoMA.

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Exterior

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We begin our approach to old Penn Station at the intersection of Seventh Avenue and 32nd Street. When the station opened in 1910, and before the subway lines were extended south along Seventh and Eighth Avenue, this was the main axis of approach. A temple front with six solid stone columns and a rectangular pediment above greeted visitors. Three eagles adorned either side of the clock, six total. After demolition, two of these eagles survive and are now placed on concrete pedestals in the adjacent plaza. Originally, one entered Penn Station at street level. Now, one descends about 20 feet to an underground corridor.

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This is the same entrance, viewed head-on from 32nd Street. Beneath this street, the Pennsylvania Railroad constructed its double-track tunnels stretching from here to Sunnyside Yard in Queens, and onward to destinations in New England and Long Island. These two tunnels survive, but everything above ground does not.

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This is the view from the 31st Street side between Seventh and Eighth Avenue. The mass of the main waiting hall rises in the center, as indicated by the arched thermal window. The colonnade at center left corresponds to the taxi and car drop-off and pick-up area. After demolition, developers erected the round mass of Madison Square Garden on the foundations of the former waiting hall and train concourse.

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This is the view from the corner of 31st Street and Seventh Avenue. Contrary to appearances, the old structure was entirely steel frame with limestone and granite facing. Only the columns on the main façades were solid stone.

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By the 1960s, the structure was sooty with car exhaust, as seen in the above photo from 33rd Street and Seventh Avenue. The rest, however, was in excellent condition.

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Shopping Arcade and Waiting Hall

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After entering Penn Station from the Seventh Avenue side, a long vaulted shopping arcade greeted visitors. The shops here were the only source of outside income for the railroad at this location. In later years, the shops did not even provide enough rent to cover the $2.5 million spent yearly on upkeep (1961 value from Ballon on p.99). Considering the size of this double-block and its prime location in Midtown, the old Penn Station generated precious little income for its owner. Currently, the lobby of Penn Plaza occupies this location — an office building with 700,000 square feet of space. Formerly public space is now rendered private. Also, note the statue of Alexander Cassatt at center right (President of the Pennsylvania Railroad).

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Proceeding down the arcade, one entered into the main waiting hall — a vaulted space about 150 feet high by ~300 feet wide. One descended a wide pair of stairs — note the statue of Cassatt in the niche. This was one of the largest internal public spaces in the city.

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This is the door into the restaurant. The arcade is on the left hand side. The stairs descending to the waiting hall are on the right hand side. Hilary Ballon writes that this “vestibule was a transitional space; it was dimly lit and nearly square to counter the directional force of the rooms on either side. It provided a moment to pause and prepare for the grand descent into the waiting hall” (p.62). This part of the building now roughly corresponds to a sub-basement buried below the walkway linking Penn Plaza to Madison Square Garden.

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This is the view down into the waiting hall. The coffered ceiling and thermal windows are modeled on the Baths of Caracalla in Rome. In the rectangular panel beneath these windows are maps of the United States and the rail networks of the Pennsylvania and Long Island Railroad. Contrary to appearances, this space contains little stone. The entire frame and support structure is of steel beams with plaster above (for the vaults) or thin limestone panels (for the walls). Ballon writes: “For those approaching from the arcade, the directional contrast in the waiting hall also created a sense of space exploding horizontally. The freestanding fluted Corinthian columns and robust curls of the acanthus leaves, the strongly projecting entablature blocks, and layered ceiling offers these sculptural features made the weightless volume of the waiting hall seem weighty. Like the plenitude of a sheltering night sky, the enormous space was both humbling and uplifting” (p.64).

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Here’s the view back up the grand stairs, this time from the waiting hall toward the arcade. The original Penn Station had no escalators from tracks to concourse or waiting areas to street level. Passengers would have had to carry their luggage up and down steep stairs; the architects of Grand Central observed this problem at Penn Station. Grand Central has ramps instead of stairs to ease movement between levels. The escalator shown in this 1960s photo is a later addition.

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This is the waiting hall in the 1962, months before demolition began. The roof and walls are visibly sooty. Where this space once stood is now a parking lot for trucks and buses using the loading dock beneath Madison Square Garden. The wall of windows at left is Penn Plaza. The sliver of building at right is the Garden.

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This older photo was taken in the morning, as the sun rose over New York, penetrating the east-facing windows, and illuminating the waiting hall. Most of the old station’s public areas and track level were touched by natural light. By comparison, no natural light enters any part of the new Penn Station. Currently, this area is a difficult-to-access parking lot — patrolled by armed guards with bomb-sniffing dogs, who shouted at me to get off what they claimed was “private property.”

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Train Concourse

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After passing through the waiting hall, visitors entered the train concourse. This was also a massive room, bathed in natural light, about ~300 feet long, ~200 feet wide, and 90 feet tall. From here, large chalkboard signage (erased and written manually) directed passengers to their right track. The above photo shows the two levels — the lower for arrivals and the upper for departures. Ballon describes the end of this journey from arcade, to waiting hall, to concourse: “The spatial compression directed attention down to the tracks, where were illuminated by natural light and visible through the cut-away floor. The vista of the sky above and tracks below created a sense of transparency in the concourse, as if the visitor was seeing with x-ray vision” (p.68).

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This 1930s photo by Berenice Abbott shows the intricate web of ironwork supporting the skylights.

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The upper level of the concourse had four exits: three minor exits north toward 33st, south to 31st, and west to 8th Avenue. The main and most ornate exit from the concourse was toward the waiting hall and 7th Avenue. Shown above is the 33rd Street exit. The wide dark exit to the right leads to the pick-up point for “Carriages and Taxicabs.”

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This is the view northwards from the 31st Street entrance to the train concourse. This photo now corresponds to the VIP entrance for spectators at Madison Square Garden.

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Here is the concourse again. In the old photo, the left exit leads to 33rd Street while the larger and arched right exit leads to the waiting hall and a baggage concourse. No trace of the old structure remains in the new photo. This is still a train concourse — except now with oppressive drop ceiling and exits to Amtrak trains.

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Many of New York’s greatest landmarks feature Guastavino Tile vaults. Penn Station too. The main area of the train concourse was covered with glass. But, the lateral row of vaults with an oculus in the center of each was made of Guastavino. No trace of these self-supporting terracotta tiles survive at Penn Station, except for a single vault at the southern exit for the local southbound One Train.

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This is the view from Track Six up past the lower concourse for arriving passengers, the upper concourse for departures, and toward the glass vaults. When this structure was demolished, Madison Square Garden was erected on the exact same bedrock foundations. The locations or number of tracks did not change, nor have the locations, width, or size of almost all stairwells. As seen in these photos, a few new supports were added to support the now much heavier structure above.

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The failure to rebuild the now grossly inadequate Penn Station is not about lack of money. Built for 200,000 commuters in 1910, today, 650,000 people go through Penn Station each day, more than the daily passengers for all three major New York City-area airports combined. The failure to rebuild is not about lack of demand either; these numbers are expected to continue growing.

This is, more than anything, a failure of political will and a lack of interest in sustaining and improving the nation’s critical rail infrastructure. The current station makes a profit for its management — from the stadium and offices above. Any new station that restores natural light to track-level and revalues the passenger experience over profit is unlikely to be as lucrative. Few tangible profits are to be made from beauty.