Complex sentence: Wilkerson had been born a slave in Virginia in 1813 and had purchased his freedom, becoming an elder of the AME Church in Cincinnati, a denomination established in 1819 and the first independent black church in the United States.
Split into simpler sentences: Wilkerson had been born a slave in Virginia in 1813 and had purchased his freedom. He had become an elder of the AME Church in Cincinnati; the denomination was established in 1819 as the first independent black church in the United States.