Julian Boilen, a full stack software engineer in NYC, created this cool map that lets you see photos of New York City in the late 1930s and 1940s. "Zoom in!" he says. "Every dot is a photo."
Between 1939 and 1941, the Works Progress Administration collaborated with the New York City Tax Department to collect photographs of every building in the five boroughs of New York City. In 2018, the NYC Municipal Archives completed the digitization and tagging of these photos. This website places them on a map.