Iconium had a Post Office during the years 1871-1959.
Missouri State Gazetteer and Business Directory, 1881:
Iconium – A sparsely settled place in Jackson Township, St. Clair County, twelve miles north east of Osceola (county seat court house), and about thirty south east of Clinton, the nearest shipping point. Weekly mail. Levi M. Gover, postmaster and farmer.
History of St. Clair Co., Missouri 1883:
Iconium is located on Section 27, Township 39N, Range 24W, lying ten miles northeast of Osceola and four miles north of Harper. A post office was opened in March 1879. C.W. Wright was postmaster in 1883, and was also a merchant, with a general store.