Complex sentence: The island, town, and Edisto River are named after the historic Edistow people, a Native American sub-tribe of the Cusabo Indians, who inhabited the island as well as nearby mainland areas.
Split into simpler sentences: The island, town and Edisto River were named after the historic Edistow people, a Native American sub-tribe of the Cusabo Indians. They inhabited the island as well as nearby mainland areas.