In 1846, James K. Polk wanted Oregon Country. He campaigned in 1844 for this area and British wouldn't agree with it so the United States negotiated this area. The United States got it in 1846.
Hillsboro, Oregon is in Washington County.
The Dalles Oregon is in Wasco county.
Yes it is the County with the largest area in Oregon.
Lincoln City, Oregon is in Lincoln County.
Tillamook County
Benton County Courthouse - Oregon - was created in 1888.
Washington County Courthouse - Oregon - was created in 1973.
Multnomah County
Eugene, Oregon is in Lane County.
Sherwood, Oregon is in Washington County.
Canby, Oregon is in Clackamas County.
Klamath County