Complex sentence: It ended both Indian and African slavery in the mainland of the Americas in the eighteenth century, but in Cuba and Puerto Rico, where sugar cane production was highly profitable based on slave labor, African slavery was abolished in 1866 and 1873, respectively.
Split into simpler sentences: It ended both Indian and African slavery in the mainland of the Americas in the eighteenth century. In Cuba and Puerto Rico, where sugar cane production was highly profitable based on slave labor, African slavery persisted until 1866 and 1873, respectively.