Over ten thousand overland immigrants reached Oregon Country between 1843 and 1851, re-settling the Willamette Valley and the Lower Columbia. By 1850, 12,093 Euro-American residents lived in Oregon. By 1860 the number grew to 52,465 settlers in Chinook country. Because waves of disease had decimated Native populations and depopulated villages, settlers saw open lands as providentially available; however, these migrants were squatters on lands to which their government had no title.

In 1843, Euro-American migrants to Oregon Country formed the Oregon Provisional Government before the U.S. had clear title to the territory. Although Oregon would not become an American territory until 1848, under the provisional governance real estate speculators made claims around the region. To satiate the growing population’s desire for land, Congress passed the 1850 Oregon Donation Land Act. This law allowed a single man to obtain a 320-acre donation land claim, with 640 available to married couples. The accompanying Indian Treaty Act of 1850 called for three Indian Agents in Oregon Territory to negotiate treaties to remove all Indians from the Willamette Valley and Lower Columbia and relocate them east of the Cascade mountains. From the Revolutionary War through the late 1860s, the United States government relied on treaties to obtain land from Native peoples as sovereign entities, usually in exchange for reserving subsistence rights and an exchange of money, goods, and services. 

From April to May of 1851 territorial superintendent for Oregon Indian Affairs, Anson Dart, and his commissioners negotiated with the Kalapuya and Molalla tribes. In June of that year the commission treated with members of the Umatilla, and travelled west to meet with the Cayuse and Nez Perce.

The Chinook also met with Dart, at Tansey Point near the Clatsop Plains, but refused to sign any agreement that removed them from their lands and ancestors. Rather, Chinook leaders reserved the community’s right to occupy their traditional homelands for the purpose of fishing, hunting, and harvesting. Between August 5 and 9, 1851 Dart made 13 treaty agreements with various groups, including those who now comprise the Chinook Indian Nation: Cathlamet, Clatsop, Lower Chinook, Wahkiakum, and Willapa. Each treaty emphasized specific places along and in the Columbia that are connected to particular bands. For example, the Tansey Point Treaty with the Kathlamet Band of Chinook points out specific islands within the Columbia River, which are not ceded.

Sources:
Jette, Melinda Marie. At the hearth of the crossed races: a French-Indian community in nineteenth-century Oregon, 1812-1859. Corvallis: Oregon State University Press, 2015.