U.S. Highway 218 (US 218) is an original United States Highway that was created in 1926. Although technically a spur of US 18, US 218 neither begins nor ends at US 18, but overlaps US 18 for eight miles (13 km) near Charles City, Iowa. US 218 begins at U.S. 136 in downtown Keokuk and ends 319 miles (513 km) away at Interstate 35 (I-35) and US 14 at Owatonna, Minnesota. A large portion of US 218 in Iowa is part of the Avenue of the Saints, which connects St. Louis, Missouri, and Saint Paul, Minnesota.

Charles City is a city in and the county seat of Floyd County, Iowa. Charles City is a significant commercial and transportation center for the area. U.S. Routes 18 and 218, Iowa Highway 14, and the Canadian National and Canadian Pacific railroads serve the city. The population was 7,396 at the time of the 2020 census, a decrease of 5.3%, from 7,812 in 2000.