Complex sentence: As in Virginia and Delaware, numerous planters in Maryland had freed their slaves in the twenty years after the Revolutionary War, and by 1860 Maryland's free black population comprised 49.1% of the total number of African Americans in the state.
Split into simpler sentences: As in Virginia and Delaware, numerous planters in Maryland had freed their slaves in the twenty years after the Revolutionary War. By 1860 Maryland's free black population comprised 49.1% of the total of African Americans in the state.