On January 22, 1855, near Mukilteo, among the signers of the Treaty of Point Elliott, the Duwamish Tribe was listed first. Chief Si'ahl's name was placed at the very top of the treaty, reflecting his personal importance and that of his tribes. The Duwamish signers of the Point Elliott Treaty were Chief Si'ahl, and the Duwamish "sub-chiefs" Ts'huahntl, Now-a-chais, Ha-seh-doo-an.
The 1855 Treaty created a Government-to-Government relationship between the United States and the Dxʷdəwʔabš. The United States Senate ratified the Point Elliott Treaty in 1859. The Treaty of Point Elliott guaranteed hunting and fishing rights and reservations to all Tribes represented by the Native signers.
In return for the reservation and other benefits promised in the treaty by the United States government, the Duwamish Tribe exchanged over 54,000 acres of their homeland. Today those 54,000 acres include the cities of Seattle, Renton, Tukwila, Bellevue, and Mercer Island, and much of King County.
European-American immigrants soon violated the Treaty of Point Elliott of 1855, triggering a series of Native rebellions from 1855 to 1858 known as "the Indian War". Instigated by the European-Americans, this war set tribe against tribe, and brother against brother. Chief Si'ahl helped protect the small group of European-American settlers from attacks by other Native warriors in what became the City of Seattle during the rebellions.