Provisional and Territorial Records Guide
Note: The following map is intended to provide researchers with a general understanding of significant county boundary changes over time. Researchers should refer to other sources for more detailed and precise representations.
Washington Territory was created by Act of Congress on March 2, 1853. By this time, the number of counties in Oregon Territory had grown to twelve and the white population to over 29,000. Eighty percent of the population lived in the northwest corner of the territory and less than 1500 people lived east of the Cascade Mountains. Oregon Territory now comprised the area south of the Columbia River and latitude 46', north of latitude 42', and between the Pacific Ocean and the crest of the Rockies.