Complex sentence: African Americans had long composed the majority of the state's population; however, in 1860, only 2 percent of the state's black population were free; most were mulattos or free people of color, with ties of kinship to white families.
Split into simpler sentences: African Americans had long composed the majority of the state's population. However, in 1860, only 2 percent of the state's black population were free; most were mulattos or free people of color, with ties of kinship to white families.