In the decades following the Civil War, the Catholic Church became the largest church in the United States. Its unprecedented and tremendous growth was due almost entirely to immigration. First Irish, and then German Catholic immigrants, dominated the Roman Catholic Church. The ethnic composition became ever more diverse as immigration peaked at the turn of the 20th century.  The middle Connecticut River Valley was home to thousands of Eastern European immigrants and this church in South Deerfield, Massachusetts, is named for the Polish Saint Stanislaus.