Troy Mills is an unincorporated community in northern Linn County, Iowa, United States. It lies along local roads north of the city of Cedar Rapids, the county seat of Linn County. Its elevation is 869 feet (265 m), and it is located at 42°17′24″N 91°40′57″W / 42.29°N 91.6825°W / 42.29; -91.6825 (42.2899905, -91.6823925). Although Troy Mills is unincorporated, it has a post office, with the ZIP code of 52344, which opened on 10 June 1867.