(a) The line dividing Marion and Yamhill Counties is a line drawn along the middle of the main channel of the Willamette River where that main channel is located on June 22, 1981. All land on the east side of the line dividing Marion and Yamhill Counties is part of Marion County.
(b) The southern boundary of Marion County and the northern boundary of Linn County commences in the middle in the main channel of the Willamette River opposite the mouth of the Santiam River; thence up the middle of the main channel of the Santiam River as it existed on April 21, 1982, to a point opposite the mouth of the north fork of the river; thence up the middle of the main channel of the north fork as it existed on April 21, 1982, to the mouth of Whitewater Creek; thence up the creek to a point where the creek crosses the section line between sections 21 and 28 in township 10 south, range 7 east, Willamette Meridian; thence due east along the section line projected to the summit of the Cascade Mountains.
(2) When the Willamette River, the Santiam River, the north fork of the Santiam River or Whitewater Creek serves as the boundary between Linn and Marion Counties in subsection (1)(b) of this section, a reference to one of these rivers or creeks refers to the middle of the river or creek as it existed on January 8, 2003, and may be further identified using coordinates and other location information determined by the affected county surveyors and filed by the appropriate counties with the appropriate county assessors and the Department of Revenue under ORS 308.225. [Amended by 1981 c.214 §1; 1985 c.122 §1; 2003 c.622 §4]
Note: In addition to the boundary described in 201.240, the eastern boundary of Marion County is the summit of the Cascade Range adjacent to parts of the western boundaries of Jefferson (see 201.160) and Wasco (see 201.330) Counties. The northern boundary of Marion County is the southern boundary of Clackamas County (see 201.030). Part of the western boundary of Marion County is the Willamette River adjacent to the eastern boundary of Polk County (see 201.270).