USAboundaries: Historical and Contemporary Boundaries of the United States of AmericaSource:
This package provides contemporary (2014) boundaries for states, counties, zip code tabulation areas, and congressional districts in the United States of America. This data is provided by the U.S. Census Bureau.
This package also provides spatial objects with historical boundaries of
states or counties in the United States of America from 1629 to 2000. It
provides data from the Atlas
of Historical County Boundaries. The copyright to the historical data used
in this package is owned by the Newberry Library, and it is included in the
USAboundariesData package under the terms of the
Attribution-NonCommercial-ShareAlike 2.5 Generic (CC BY-NC-SA 2.5) license.