The U.S. Census Bureau's interactive mapping website for mapping demographic information. Easy to use!
Social Explorer (Free Edition)
Interactive maps on a variety of subjects with data from several censuses can be quickly created using Social Explorer's free edition.
Policy Map (Free Edition)
Created by a nonprofit organization called The Reinvestment Fund, PolicyMap is a Geographic Information System and mapping company. With the free version of PolicyMap, you can use a wide range of publicly available data to easily create maps.
Atlas of the Historical Geography of the U.S.
This website, created by the University of Richmond, is a digital edition of Charles O. Paullin and John K. Wright's Atlas of the Historical Geography of the United States, first published in 1932. The digital edition reproduces all of the atlas's nearly 700 maps. Many of the maps are enhanced in ways impossible in print, animated to show change over time or made clickable to view the underlying data.