Old Union was founded in 1806 under the leadership of Rev. Matthew Williams and in affiliation with the Reformed Presbyterian Church (Covenanter). The congregation met in a grove of trees about four miles north of the present location, near the present village of Brownsdale until 1820, when they moved to a site one and a half miles south of the current building.

The congregation split in 1833, and formed the North Union Reformed Presbyterian Church (Convenanter)of Forward Twp. into what was designated as the "New School" and the "Old School" as the Reformed Presbyterian Church debated participation in civil government.

In 1839 the Old Union church moved to the present site, and in 1859 changed denominational affiliation to become part of the newly-organized United Presbyterian Church of North America.

After a fire destroyed the church building in 1905, the present building was erected. In 1958 an addition was erected

The grave of James Glover, a Revolutionary War veteran and the first permanent white settler in Butler County, is located in Old Union's cemetery.

Old Union was founded in 1806 under the leadership of Rev. Matthew Williams and in affiliation with the Reformed Presbyterian Church (Covenanter). The congregation met in a grove of trees about four miles north of the present location, near the present village of Brownsdale until 1820, when they moved to a site one and a half miles south of the current building.

The congregation split in 1833, and formed the North Union Reformed Presbyterian Church (Convenanter)of Forward Twp. into what was designated as the "New School" and the "Old School" as the Reformed Presbyterian Church debated participation in civil government.

In 1839 the Old Union church moved to the present site, and in 1859 changed denominational affiliation to become part of the newly-organized United Presbyterian Church of North America.

After a fire destroyed the church building in 1905, the present building was erected. In 1958 an addition was erected

The grave of James Glover, a Revolutionary War veteran and the first permanent white settler in Butler County, is located in Old Union's cemetery.