Given a documentary edition with settlements and regions spanning the American founding era--documents originating from and correspondences delivered to place names which may no longer exist--is there open data on historical places in order to map to cities in the modern world? If there's nothing for GIS then coordinates could be added in preprocessing before loading into database for a geospatial query, so that is not a requirement of the data, it could be any taxonomy or ontology.
The Atlas of Historical County Boundaries (AHCBP) at the Newberry Library covers historical/modern, and is a geospatial open dataset.
"The Atlas presents in maps and text complete data about the creation and all subsequent changes (dated to the day) in the size, shape, and location of every county in the fifty United States and the District of Columbia. It also includes non-county areas, unsuccessful authorizations for new counties, changes in county names and organization, and the temporary attachments of non-county areas and unorganized counties to fully functioning counties. The principal sources for these data are the most authoritative available: the session laws of the colonies, territories, and states that created and changed the counties."