State highway in Washington, United States
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.