The U.S. Census Grids provide raster data sets that include not only population and housing counts, but a wide variety of socioeconomic characteristics. These gridded data sets transform irregularly shaped census block and block group boundaries into a regular surface – a raster grid – for faster and easier analysis.
S. Ahern, M. Naaman, R. Nair, and J. Yang. JCDL '07: Proceedings of the 7th ACM/IEEE-CS joint conference on Digital libraries, page 1-10. New York, NY, USA, ACM, (2007)