Church of the Assumption in Ansonia, Connecticut, is a Catholic parish founded on June 25, 1870. Originally part of St. Mary's Parish in Derby, Fr. John Sheridan began efforts to establish a dedicated church, leading to the laying of the cornerstone on August 15, 1867. The first structure, completed in 1868, was named “The Church of the Assumption of the Blessed Virgin Mary,” and by 1890, the parish had grown to nearly 4,000 parishioners.