The United States federal government left their part of the region unorganized for two years until news of the Whitman massacre reached the United States Congress and helped to facilitate the organization of the region into a U.S. territory . On August 14 , 1848 , Congress passed the Act to Establish the Territorial Government of Oregon , which created what was officially the Territory of Oregon . The Territory of Oregon originally encompassed all of the present-day states of Idaho , Oregon and Washington , as well as those parts of present-day Montana and Wyoming west of the Continental Divide . Its southern border was the 42nd parallel north ( the boundary of the Adams-Onis Treaty of 1819 ) , and it extended north to the 49th parallel . Oregon City , Oregon , was designated as the first capital
Whitman massacre
Whitman massacre
Oregon Territory