Before February 28, 2000 the township was named Union Township for almost two hundred years. Increasing urbanization and development led more people to refer to West Chester as a name for the area. On March 1, the name was formally changed. Note: many census and government records (including the 2000 census) will still refer to Union Township.
As of 2000 the population is 42,764 which includes the population of the unincorporated villages of Beckett Ridge, Olde West Chester, and Wetherington.
The original extent of Union Township has been reduced by the annexation of the south central township by the city of Sharonville.