By 1840 more than 15,000 people were members of abolitionist societies. Abolitionism became a popular expression of moralism and a factor that led to the war. In churches, conventions, newspapers, abolitionists advocated an immediate end to slavery. The issue split religious groups, with even the main denominations forming rival Southern and Northern churches as the war approached. In 1845 the Baptists split over slavery into the Northern Baptists and Southern Baptists.