Washington State Route 501

State Route 501
Erwin O. Rieger Memorial Highway
The existing highway is highlighted in red. The proposed completion is shown in dashed purple.
Route information
Auxiliary route of I‑5
Defined by RCW 47.17.640
Maintained by WSDOT
Length:	13.97 mi (22.48 km)
Existed:	1964 – present
Southern section
Length:	11.00 mi (17.70 km)
South end:	I‑5 in Vancouver
North end:	Ridgefield NWR near Vancouver
Northern section
Length:	2.97 mi (4.78 km)
West end:	Main Street in Ridgefield
East end:	I‑5 in Ridgefield
Location
Counties:	Clark
Highway system
State highways in Washington Interstate US State Scenic Former PSH 1964 renumbering Former ← SR 500 SR 502 →

State Route 501 (SR 501, designated as the Erwin O. Rieger Memorial Highway) is a 13.97-mile-long (22.48 km) state highway in the southern part of the U.S. state of Washington. It is split into two sections in Clark County, a north–south alignment connecting Interstate 5 (I-5) in Vancouver to the Port of Vancouver and the Ridgefield National Wildlife Refuge, and a west–east alignment connecting Ridgefield to I-5. Prior to the 1964 highway renumbering, SR 501 was designated as Secondary State Highway 1T (SSH 1T), established in 1937 and re-aligned to serve the Port of Vancouver in 1963.

The 11.00-mile-long (17.70 km) southern section of SR 501 and the Erwin O. Rieger Memorial Highway begins as the four-lane Mill Plain Boulevard at a diamond interchange with I-5 in Downtown Vancouver. The highway travels west through Downtown Vancouver and splits into a one-way pair on 14th Street and 15th Street before rejoining as Mill Plain Boulevard. SR 501 crosses a BNSF rail yard and enters the Port of Vancouver, becoming the Lower River Road and narrowing to a two-lane highway on the south side of Vancouver Lake. The highway follows the Columbia and Lake rivers north past the Shillapoo Wildlife Recreation Area, ending south of Post Office Lake in the Ridgefield National Wildlife Refuge.