II.Protestants in the United States The Baptists are the largest Protestant group.They believe in adult baptism by immersion,symbolizing a mature and responsible conversion experience.In 2009,the denomination had 1.3 million members in over 5000 churches in the US.(Below is the newly built Fairview Baptist Church in South Carolina)II. Protestants in the United States • The Baptists are the largest Protestant group. They believe in adult baptism by immersion, symbolizing a mature and responsible conversion experience. In 2009, the denomination had 1.3 million members in over 5000 churches in the US. (Below is the newly built Fairview Baptist Church in South Carolina)