U.S. Surveyor General's Records for Illinois -- Federal Township Plats

Illinois Library Field Notes and Plat Maps, 1804 to 1862

County Surveyors in Illinois

https://catalog.archives.gov/id/66587517

https://idaillinois.org/digital/collection/IllinoisPlats/search

Outdoor Illinois Journal: "More than a Map: The Legacy of Illinois' First Public Land Surveys" 

Survey chain

List of Cartographic Records of General Land Office

BLM Records