Adair is a city in Adair and Guthrie counties of Iowa in the United States. The population was 791 at the 2020 census. The Rock Island Railroa…Adair is a city in Adair and Guthrie counties of Iowa in the United States. The population was 791 at the 2020 census. The Rock Island Railroad was built through the area in 1868, which led to the area being known as Summit Cut. This was in reference to the ridge that forms the watershed divide between the Missouri and Mississippi rivers. The town officially became known as Adair on August 20, 1872, when it was incorporated with the county. The town is named after General John Adair, a general in the War of 1812 who later became the eighth governor of Kentucky. Adair was the scene of the first successful train robbery in the American West when on July 21, 1873, the James-Younger Gang took US $3,000 from the Rock Island Express after derailing it southwest of the town. The derailment killed the engineer.