With technology like Google Street View at our fingertips, it’s easy to take a visual catalog of relatively mundane New York City architecture — its doors — for granted. But Roy Colmer’s 3,000 photographs in “Doors, NYC,” aren’t a product of the digital age; they’re a meticulous and demanding undertaking that paint a portrait of the city’s streets in the 1970s. The project is now available online via the New York Public Library, and was recently publicized by NPR.

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Colmer shot the city’s entranceways between November 1975 and September 1976 on “120 intersections and streets of Manhattan from Wall Street to Fort Washington,” according to Stephen C. Pinson, the library’s curator of photography. What’s most intersting about the collection is the way he photographed and organized the images. “Rather than approaching the task in a predetermined order,” Pinson notes, “Colmer instead photographed the city as he moved through it on a daily basis, often by subway, from one neighborhood to another, and from one block to the next.” He then took notes about each path, including the side of the street he was on, and organized the collection in terms of those indexes. If you look closely, you can even see Colmer’s reflection in some of the doorways.

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While Colmer’s exhibition has toured elsewhere, the NYPL is the “only institution with a complete set” of the project. View the full collection here.

(Photo: Roy Colmer/NYPL)