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The changing boundaries of Black Harlem
The lines labeled Black Harlem 1920, 1925, and 1930 encompass the area of Harlem in which the population was entirely black, a combination of African Americans and West Indian immigrants. Blacks lived beyond those boundaries as well, in smaller proportions.
The boundaries lines are based on maps in Gilbert Osofsky, Harlem: The Making of a Ghetto (1971) & James Weldon Johnson, Black Manhattan (1930), and are derived from the Federal censuses of 1920 and 1930, and the New York State census of 1925.
The Bromley Real Estate Map overlay
The overlaid map of individual buildings is made up of plates from our copy of the Atlas of the City of New York, Borough of Manhattan, Vol. 4 & 5, published by G W Bromley & Co. in 1932. Our copy of the atlas was updated to 1940 – which means that changes that took place were literally pasted on top of what was present in 1930. We have replaced all the changes we could identify with what was present in 1930; changes that took place during the 1920s are noted in the records of each address. The map displays the footprint of each building in Harlem, together with information on the number of floors, the presence of shops, and the material from which the building was constructed. See the key below:
Digital Harlem Blog 