City Tech Library has a collection of maps created by the Sanborn Map Company (2000) useful for research about NYC buildings.
Paper copies of the following are on Reserve in the library -- ask at the Circulation Desk:
Manhattan (between 34-46th Streets and 1st and 2nd Avenues: maps 24, 26, 35-38
Brooklyn: maps 5, 6, 18, 24-25, 28-30, 35
Electronic copies of the following are available in the Multimedia Resource Center:
DWG maps: Brooklyn maps 24, 25, 35
TIF maps: Brooklyn maps 22, 23, 27, 31