I've been exploring the NYPL's Digital Collections archives for some time now, and yesterday the library released a new search tool, an interactive map, OldNYC.org, that makes it easy to sample its collection of historic photographs by neighborhood.
Anyone living in the South Slope/Greenwood/Gowanus/South Brooklyn (etc. etc.) area should be able to recognize the location in this Percy Loomis Sperr photograph, taken in 1930. Any takers?