Home | Atlas of Historical County Boundaries Project

Interactive Maps Are Back
This site now features new and improved interactive maps showing county border changes.
This site is in testing mode, we welcome your feedback; please email us.

State Data

Select a state from the map to view all of the Atlas' content related to that state, including shapefiles, chronologies, and metadata.

If you are having trouble viewing the map or clicking on it, try the list of states page.

National Data

Click the map above for national data files, historical commentary, and metadata are also available.

Boundary Animations

US Historical State & Territorial Boundaries, 1783-2000 (3:00)
US Historical County Boundaries, 1629-2000 (0:30)
US Historical County Boundaries, 1629-2000 (3:00)
US Historical County Boundaries (1629-2000), with State/Territorial boundaries (1783-2000) (0:30)
US Historical County Boundaries (1629-2000), with State/Territorial boundaries (1783-2000) (3:00)
US Historical State & Territorial Boundaries, 1783-2000 (0:30)
US Historical State & Territorial Boundaries, 1783-2000 (3:00)
US Historical County Boundaries, 1629-2000 (0:30)

Atlas of Historical County Boundaries

On March 31, 2025, a critical component of the AHCB interactive map technology will be retired by one of our third-party vendors. We are actively working to rebuild the technology and minimize any downtime for the maps. During this transition, data files will remain available for download and use.

State Data

National Data

Boundary Animations