State and Federal taxation records are available on microfilms through Family History Centers. There are county records. Go to the counties in question.
Oregon Internal Revenue Assessment lists 1867-1873
United States, Bureau of Internal Revenue, microfilmed by the Genealogical Society of Utah, 1989 at the National Archives Records Administration - Seattle, Washington Branch. Some years missing.
Assessment lists 1867-1870 - (Family History Library film 1639854 item 3-10).
Assessment lists 1871-1873 - (Family History Library film 1639855 item 1-4).
"Oregon memorial of citizens of the U. S. and miscellaneous information : census records for 1843, tax rolls, newspaper clippings of Oregon pioneers, government document on the boundry line between the British and United States territories in Northwestern America". (Family History Library film 430055 item 3).
A wiki article describing an online collection is found at: