- 631 Topeka Avenue | PO Box 361 | Lyndon, KS 66451 | (785) 828-3477 (located just south of the courthouse) Welcome Researchers and Genealogists! If you plan to do research in Osage County, Kansas, let the experienced staff of the Osage County Historical Society & Research Center help you find your family's history. They have access to: Early settlers of Kansas pedigree charts Index to Osage ...www.osagechs.org