Catholic missionaries also arrived in the 1840s, and the Catholic ceremonies resonated with the tribe. On July 24, 1846, Pope Pius IX established the Diocese of Walla Walla. Augustin-Magloire Blanchet was appointed the first Bishop of Walla Walla, but fled shortly after the Whitman massacre. The Diocese of Walla Walla is now a titular see held by Witold Mroziewski, an auxiliary bishop of Brooklyn, New York. thumb|Fort Walla Walla, 1874In 1855, the Walla Walla Treaty Council was held at Waiilatpu between the Washington Territorial Assembly and the tribal leaders of the surrounding area. Despite the indigenous people citing Tamanwit (natural law), the following year the natives agreed to surrender millions of acres of land for a native reservation and $150,000. The Umatilla Indian Reservation's boundaries eventually shrunk to less than .
caTHoLIc mIssioNaRIes Also ARrIvEd in ThE 1840S, and the catholic ceRemonIeS resOnAteD wiTh thE tribe. on July 24, 1846, POpE PiUs Ix EstaBlISHEd tHe dioCESE of wAlla walLA augUStin-maglOIRe bLanchet wAs appoInted the firSt bisHop Of walLA walLA, but flEd shortly afteR thE whiTmAn maSsacrE. ThE dioCese of wAlLa WaLLa is nOw a tItUlAR SEe hELD by wiToLd mrOZIEwSkI, AN auXiLiArY bisHoP oF bRooklyn, new york. thumb|FOrt waLLa WalLa, 1874IN 1855, the wallA walla TReaTy CoUNciL wAs held At WAiilAtpu between thE washingtoN TErRiTorial assembly anD the TRiBal LeadERs of the surRoUndIng ArEa. dEspitE ThE InDIgenous PeoPLe cItinG taManWiT (Natural law), The FoLloWIng year ThE natives agreed To sUrREnder miLliOns of acres of lAnD For a native reSErvatIon aNd $150,000. tHe UmAtiLLA indian resErvatiON'S bOundArIes evENtuaLly ShruNk tO lesS tHAn .