Records at Oregon Secretary of State Historical Records Index
 Census records 1849 - 1858
 Tax Rolls 1853 - 1859
 1849 Oregon Territorial Census, March 1849: Clatsop County Alphabetical
 1849 Oregon Territorial Census, March 1849; Clatsop County By Page

In the links below, once you click on a link and the resulting pages are returned,  you can narrow your search by entering names in the  first and or last name fields on the left hand side of the page and then clicking on the 'Update' button.
1850
1860

Unfortunately, for 1870 they did not index by county so you have to search the entire state.  You really need to filter by unique first and last name to narrow it down.

1870

In the links below, once you click on a link and the resulting pages are returned,  you can narrow your search by entering names in the  first and or last name fields on the left hand side of the page and then clicking on the 'Update' button.
1880
1900
1910
1920
1930
1940