The Union Cemetery, also known as the Riverside Cemetery, was donated to the Knox Presbyterian Church congregation by a Mr. Duncan Carmichael shortly after Confederation in 1867. The donated land, to be used as a burial ground, was taken from the surrounding lands farmed by Mr. Carmichael, a Scottish settler to Thorah Township.

The first burials at the cemetery were the children of Duncan and Flora Carmichael in September, 1851 (Catherine - age 5 and Donald - age 14). The cemetery contains 30 stones although it has been noted that many of the stones have been lost due to the Beaver River or broken. 107 persons are known to have been buried in the cemetery.

The cemetery was operated as a by the church congregation until the 1960's when it was turned over to the former Township of Thorah.