From Portland South:

Take Highway 26 West to Seaside. Go North on Highway 101 through Seaside. Go straight through the light at Ensign and take your next right. Continue to Fort Clatsop road, turn right, the entrance will be on your left.

From Portland North:

Take I-5 or Highway 205 North to Longview. Take the first exit to Longview (Highway 432 or the truck route) follow truck route signs to Highway 433 turn left and take the BIG bridge over the Columbia River. Turn right onto Highway 30 West to Astoria. From I-5 to Astoria is approximately 50 miles. Go through Astoria and go south on Highway 101. Take the first left, Marlin Ave., after you have crossed the Youngs Bay Bridge (you will come to a new stop light, 3rd one after the bridge, just south of Fred Meyer). Take Marlin Ave. to Alternate (Business) 101, turn left, follow the signs to the park. Turn right onto Fort Clatsop Road. The entrance will be on your left.