The yakama nation signed major treaties at which 1855 conference

The reservation was created in 1855 by a treaty signed by the Governor of the Washington Territory, Isaac Stevens, and representatives of the Yakama tribe. Several native leaders thought that those representatives did not have the authority to cede communal lands and did not obtain a true consensus in the council or in the tribe. A dispute over the treaty led to the Yakima War (1855-1858) against the United States.

not sure might be he acquired the entire oregon territory from great britain

no options provided, here,but the answer to this question is often: a historian cites a japanese newspaper article published a year after the end of world war ii in order to draw conclusions about the effect of the war on the japanese economy.

clearly from the answer, the historian alludes to historical sources,and records to aid in analyzing and drawing conclusion on the effect of the war on the economy of japan.