Union Mills is an unincorporated community in Mahaska County, in the U.S. state of Iowa.

[1] A post office was established at Union Mills in 1848, and was discontinued in 1857.

The post office was reestablished in 1863 and was discontinued in 1907; it was briefly known as Widow's Home.

[2] The population of Union Mills was estimated at 50 in 1887,[3] was 60 in 1902,[4] and was 52 in 1925.

This article about the geography of Mahaska County, Iowa is a stub.