Catholic missionary Eugene Casimir Chirouse traveled from his native France to Oregon Territory with four missionary oblates and arrived at Fort Walla Walla on October 5, 1847—only a month before the killings at the Whitman Mission. The Catholic fathers and missionaries were now called upon to be peacemakers.

Chirouse was ordained at Hudson's Bay Company Fort Walla Walla on January 2, 1848, the first Catholic ordination in what would become the state of Washington. 

In 1853, Fr. Chirouse founded the St. Rose of the Cayouse mission at the mouth of Yellowhawk Creek, where Governor Isaac Stevens met him on his way from the east through the Walla Walla Valley to assume his duties in Olympia. Chirouse was also present at the Walla Walla Treaty Council of 1855 conducted by Stevens. 

At the end of 1856, during the Indian Wars, he was transferred to the Puget Sound area, where he lived and worked for most of the rest of his life, dying in British Columbia in 1892.

Eugene Chirouse is portrayed by Jean-Paul Grimaud.