Christianity was introduced to the Americas as it was first colonized by Europeans beginning in the 16th and 17th centuries. Immigration further increased Christian numbers. Going forward from its foundation, the United States has been called a Protestant nation by a variety of sources. When the categories of “irreligion” and “unaffiliated” are included as religious categories for statistical purposes, Protestants are technically no longer the majority in the United States; however, this is primarily the result of an increase in Americans professing no religious affiliation, rather than being the result of an increase in non-Protestant religious affiliations, and Protestantism remains by far the majority or dominant form of religion in the United States among American Christians and those Americans who declare a religion affiliation. Today, most Christian churches in the United States are either Mainline Protestant, Evangelical Protestant, or Catholic.