Originally named Puddleville, Adel, the county seat of Cook County, incorporated on October 3, 1889. Local stories speculate that the city's first postmaster, Joel "Uncle Jack" Parrish, saw the name "Philadelphia" on a crocus sack and struck out the first and last four letters to create the present name of Adel.
The Jim Paulk-Sowega Building, built in the 1930s, now houses the Adel-Cook County Chamber of Commerce. The building, also known as the Watermelon Building, has an exterior of green watermelon motifs.
The U.S. Post Office on Parrish Street in Adel houses a New Deal-era mural, "Plantation Scene", painted in 1941 by Alice Flint.
Reed Bingham State Park lies eight miles west of Adel. This park surrounds a 375-acre lake known for boating and water skiing. Camping, fishing and picnicking are also offered at this facility.