The Digital Harlem website presents information, drawn from legal records, newspapers and other archival and published sources, about everyday life in New York City's Harlem neighborhood in the years 1915-1930.
Data does not appear to be available for download, but the site is searchable by a number of facets, including personal names, events, and places. This is a a visually appealing and easy to use online mapping application.
For more information visit the Digital Harlem blog.
The National Historical Geographic Information System (NHGIS) provides, free of charge, aggregate census data and GIS-compatible boundary files for the United States between 1790 and 2010.