Atlas of Historical County Boundaries Project
The Atlas of Historical County Boundaries, a project of the William M. Scholl Center for American History and Culture at The Newberry Library, is an electronic reference tool for historical research. It provides detailed maps and data on the creation and changes of U.S. county boundaries, including non-county areas, failed county proposals, name changes, and temporary attachments. The primary sources are official session laws from colonies, territories, and states.