The number of Catholics grew from the early 19th century through immigration and the acquisition of the predominantly Catholic former possessions of France, Spain, and Mexico, followed in the mid-19th century by a rapid influx of Irish, German, Italian and Polish immigrants from Europe, making Catholicism the largest Christian denomination in the United States. This increase was met by widespread prejudice and hostility, often resulting in riots and the burning of churches, convents, and seminaries. The integration of Catholics into American society was marked by the election of John F. Kennedy as President in 1960. Since then, the percentage of Americans who are Catholic has remained at around 25%.