The first Catholics to arrive were Jesuit missionaries seeking to convert the Huron Indians in the 17th century. Protestant settlers and missionaries of different sects, including large numbers of German Lutherans, came during the 19th century, along with Protestants from the east. Jews settled primarily in the cities. These groups often had conflicting aims. Evangelical sects favored strict blue laws and temperance legislation, which was enacted in many communities. The use of Protestant prayers and the King James Bible in public schools was another source of public discord until these practices were declared unconstitutional by the state supreme court in 1890. A constitutional amendment allowing parochial school students to ride in public school buses was defeated in 1946, amid great controversy; 19 years later, however, it was enacted with little opposition. By that time, religious conflicts appeared to be on the decline.
In 2000, there were 1,695,680 Roman Catholics in Wisconsin. Lutherans make up the largest Protestant group, though they are divided in denominations: the Evangelical Lutheran Church in American, 463,432; the Lutheran Church—Missouri Synod, 241,306; and the Wisconsin Evangelical Lutheran Synod, 241,306. Other leading Protestant groups include the United Methodists, 129,216, and the United Church of Christ, 83,768. There were an estimated 28,230 Jews in 2000, primarily in the Milwaukee area. The Muslim population had about 7,796 members. Though still relatively small in total membership, the Salvation Army reported growth from 2,574 members in 1990 to 12,951 members in 2000, a difference of 403%. Over 2.1 million people (about 39% of the population) were not counted as members of any religious organization.