Each X.tract10 is a
SpatialPolygonsDataFrame with polygons made from the 2010 US Census tiger/line boundary files (http://www.census.gov/geo/www/tiger/) for Census Tracts. It also contains 461 variables from the Summary File 1 (SF 1) which contains the 100-percent data (http://www.census.gov/prod/cen2010/doc/sf1.pdf).
Author: Zack W Almquist
Maintainer: Zack W Almquist <firstname.lastname@example.org>
Census 2000 Summary File 1 [name of state1 or United States]/prepared by the U.S. Census
Zack W. Almquist (2010). US Census Spatial and Demographic Data in R: The UScensus2000 Suite of Packages. Journal of Statistical Software, 37(6), 1-31. http://www.jstatsoft.org/v37/i06/.