South Union Mennonite Church was formed in 1845 out of the Amish settlement in Logan County. In the early years the church met in various members homes until the first building was erected in 1857 in Liberty Township, about ¾ miles northwest of the present building. On June 7, 1863 the first permanent Sunday School in the Old Mennonite church was established at South Union. Sunday School continues to be a vital part of the worship experience at South Union Mennonite Church.

Over the years South Union has been generous in supporting missionary activities. Even through different building programs that church continued to support the mission activities of the Mennonite Board of Mission.

The present facility of South Union, located directly north of West Liberty at the corner of State Route 68 and 508, was dedicated on November 15, 1953. It has recently undergone some remodeling to keep it attractive and functional. It includes handicap accessibility to the basement and main floors with handicap restrooms on the main floor.