Washington State Route 401

State Route 401
SR 401 is highlighted in red.
Route information
Defined by RCW 47.17.580
Maintained by WSDOT
Length:	12.13 mi (19.52 km)
Existed:	1964 – present
Tourist routes:	Lewis and Clark Trail Scenic Byway
Major junctions
South end:	US 101 in Megler
North end:	SR 4 in Naselle
Highway system
State highways in Washington Interstate US State Scenic Former PSH 1964 renumbering Former ← SR 397 I‑405 →

State Route 401 (SR 401) is a 12.13-mile (19.52 km) long state highway in Pacific County within the U.S. state of Washington. The highway originates at the north end of the Astoria–Megler Bridge west of Megler at an intersection with U.S. Route 101 (US 101). The roadway travels northeast, paralleling cliffs, the Columbia River and the South Fork of the Naselle River to Naselle, ending at SR 4. The road was designated Secondary State Highway 12B (SSH 12) between 1937 and 1964, when SR 401 was created to replace SSH 12B. The Astoria–Megler Bridge, completed in 1966, replaced a ferry east of the bridge, where the highway originally ended, and is known locally as Kingston Ferry Road. The roadway was extended west to the north end of the bridge, where it currently terminates. The former ferry terminal became the Dismal Nitch rest area, named after the Lewis and Clark Expedition's description of the place.

SR 401 originates at an intersection with U.S. Route 101 (US 101) at the north end of the Astoria–Megler Bridge west of Megler and southeast of McGowan. Traveling northeast between cliffs and the Columbia River past the Dismal Nitch Safety rest area to Knappton, the highway turns north along more cliffs and the South Fork of the Naselle River. In Naselle, the South Fork merges with the Naselle River, which the roadway crosses over three times before terminating at SR 4. The intersection with SR 4 is also the busiest segment of the road with an estimated daily average of 2,800 motorists, which has been decreasing from 3,100 motorists in 2005.