Allen County, KS is located in the southeastern portion of Kansas, bordered by Anderson and Woodson counties to the north, Coffey County to the east, Greenwood County to the south and Wilson county to the west. It was named after former U.S. Vice President William Allen and was established in 1855. The county seat is Iola and its largest city is Humboldt. The population is 13,371 people according to 2019 estimates. Allen County covers 565 square miles and has a mainly agricultural economy with some oil production activity in rural areas.