Land for sale in Monona County recently totaled $4 million and nearly 1,000 acres. Monona County ranks 94th out of 99 counties in the state for the total number of acres of land currently advertised for sale. Onawa featured the most land for sale. Monona County has a large agricultural economy, with 538 farms recorded in the county during the latest U.S. Census. Farming activities in Monona County generate annual revenues of $23 million, most of which is from crops. Monona County is Iowa's 16th largest county (698 square miles). It's located in the Western Iowa region of Iowa.