Union Township was the 13th and last township formed in Butler County. It was authorized June 2, 1823, by Butler County commissioners. Its land was taken from Liberty Township. The 1875 atlas said "its name was given it with no historical significance." It became West Chester Township June 28, 2000, 90 days after the Butler County Board of Elections certified the result of a March 7, 2000, vote. The name change was approved by 86.5 percent of the voters -- 11,666 in favor, 1,826 against. Before the name change, it was one of 28 Union townships in Ohio's 88 counties.