The Suquamish remained peaceful with the whites but had many conflicts with other tribes. They fought with the Duwamishes because they wanted their land. The two tribes reduced in population partly because of the Suquamish aggressions. They traded with surrounding tribes and with Hudson's bay company at Fort Nisqually. The tribe came under influence of Roman Catholic missionaries in the late 1830s. The tribe is a party to the Point Elliott Treaty. The treaty established the 7,284.48-acre Port Madison Reservation. Their chief Kitsap disagreed with the treaty and chose not to live there. When allotment started 5,909.48-acres was allotted to thirty-nine Indians and 1,375 acres went unallotted. By an act of Congress on October 24, 1864 the reservation was enlarged and redefined. The people farmed very little on their allotments. They retained their fishing and hunting life-styles.
The tribe is governed by the elected seven-member council. Their constitution and bylaws were adopted on May 23, 1965. In the case Oliphant v. Suquamish Tribe the United States Supreme Court ruling ruled that "Indian Tribal Courts do not have inherent criminal jurisdiction to try and to punish non-Indians, and hence may not assume such jurisdiction unless specifically authorized by Congress to do so." This came up because there are so many non-Indians living on the Port Madison reservation. The tribe filed a claim for additional compensation for lands ceded to the United States under the Point Elliott Treaty. There was 87,130 acres ceded to the United States. The fair market value of that land was $78,500 in 1859. The final judgment was October 22, 1970 and the commission ruled they should receive $36,329.51 for the lands ceded. Consequently the commission decided on January 21, 1996 the tribe was entitled to an additional $42,170.49. The reservation remains at 2,849.42 acres in trust or in Indian ownership.