High Quality Content by WIKIPEDIA articles! St. Clair Township, one of thirteen townships in Butler County, Ohio, United States, consists of three disconnected pieces located along the Great Miami River in central Butler County. It had a population of 7,336 in 2000, down from 7,670 in 1990. Exclusive of the village of New Miami, which lies within its borders, the unincorporated portion of St. Clair Township had 4,608 inhabitants in 2000.