Please note: the interactive map portion of this site is temporarily unavailable.
A beta version of the rebuilt interactive maps has gone out to testers. We hope to return this important feature soon.
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Using the Atlas

The Atlas of Historical County Boundaries is meant to be a resource for people seeking records of past events, and people trying to analyze, interpret and display county-based historical data like returns of elections and censuses, and for people working on state and local history projects. The special interests of those potential users range from history to demography, economics, genealogy, geography, law, and politics. The downloadable data can be used with various GIS (Geographic Information Systems) programs to create specialized projects.

ArcIMS Interactive Map Website temporarily unavailable

Arc IMS image of Washington state

The Web site for the Atlas of Historical County Boundary Project provides interactive maps for all states. These maps were created using ArcIMS software from Environmental Systems Research Institute (ESRI), and they can be accessed using the Internet Explorer or Mozilla Firefox browsers. No downloads are required to view the maps.

The interactive maps make use of the date-coding incorporated in the county boundary data. The maps allow the user to select any date and display the county configuration at that date. Several additional map layers are provided, including modern county seats, unsuccessful county proposals, modern county boundaries, and state boundaries. Each of these layers can be toggled on or off by the user.

The interactive maps provide a variety of map navigation tools, along with query tools to allow the user to obtain additional information about each county. The interactive maps also provide links to supplemental documents showing, among other items, the combined chronology of the state's county boundary changes, and the chronologies of each individual county's changes.