Complex sentence: After the American Civil War, another split occurred when most freedmen set up independent black congregations, regional associations, and state and national conventions, such as the National Baptist Convention, which became the second-largest Baptist convention by the end of the 19th century.
Split into simpler sentences: After the American Civil War, another split occurred when most freedmen set up independent black congregations. Many set up their own Baptist churches, regional associations, and state and national conventions, such as the National Baptist Convention, which became the second-largest Baptist convention by the end of the 19th century.