United States Census Maps
1990 forward : At the Census Bureau Tiger Mapping internet site there are several different sections to view: U.S. Census Bureau's Mapping and Cartographic Resources: http://www.census.gov/geo/www/tiger/index.html
County boundaries changed often over the years, these maps show the county boundaries for each of the census years.
United State Census Bureau
A new Census Atlas is now available online from the United States Census Bureau
Census Atlas of the United States, the first comprehensive atlas of population and housing produced by the Census Bureau since the 1920s. The Census Atlas is a large-format publication about 300 pages long and containing almost 800 maps. Data from decennial censuses prior to 2000 support nearly 150 maps and figures, providing context and an historical perspective for many of the topics presented.
A variety of topics are covered in the Census Atlas, ranging from language and ancestry characteristics to housing patterns and the geographic distribution of the population. A majority of the maps in the Census Atlas present data at the county level, but data also are sometimes mapped by state, census tract (for largest cities and metropolitan areas), and for selected American Indian reservations. The book is modern, colorful, and includes a variety of map styles and data symbolization techniques.
United States Census Bureau State and County Map. This map will allow you to zoom in on any state or county in the United States and read the names of all of the neighboring counties. This map shows only current counties and not historical counties.