Complex sentence: The Mohegan are a Native American people historically based in present-day Connecticut; the majority are associated with the Mohegan Indian Tribe, a federally recognized tribe living on a reservation in the eastern upper Thames River valley of south-central Connecticut.
Split into simpler sentences: The Mohegan are a Native American people historically based in present-day Connecticut; the majority are associated with the Mohegan Indian Tribe. The tribe are federally recognized, and live on a reservation in the eastern upper Thames River valley of south-central Connecticut.