Complex sentence: The Stillaguamish Tribe, a party to the Treaty of Point Elliott of 1855, became federally recognized in 1976, but lacked a reservation and had limited revenue from small commercial ventures.
Split into simpler sentences: The Stillaguamish Tribe was a party to the Treaty of Point Elliott of 1855. The tribe became a federally recognized tribe in 1976, but lacked a reservation and had limited revenue from small commercial ventures.