While the entire Oregon coast is pretty amazing, from PDX the closest beaches are found heading west on Rt. 26 which is highlighted on this Oregon's North Coast Plank Map.  Pick up US 101 in Astoria, the first settlement west of the Rocky Mountains and Oregon's oldest city founded in 1811, and head south towards Cannon Beach and Haystack Rock, which if done properly, this ~25 mile drive should take a full day.

While Astoria is a multi day stay unto itself, start your morning at Coffee Girl on Pier 39 which is the oldest waterfront building in Astoria hailing from it's days as the salmon canning capital of the world.  From there head west out of town on 101, but shortly outside of town detour off 101 to Fort Stevens State Park to do some exploring.  That's easily a full morning before you head south to Seaside for lunch.  After lunch you can either head down to the beach, do some shopping or stroll along the ~1.5 mile Seaside Promenade (aka Prom).

From there you head back out to 101 south towards Cannon Beach, but before getting into town visit Ecola State Park.  Stunning views that you might remember from the Goonies and then a drive into Cannon Beach for dinner, drinks and a sunset walk along the beach past Haystack Rock.  Now that's a day well spent.

Plank maps are made from .75" thick premium pine to ensure a clean and beautiful look, the dimensions are 11" W x 16" H and come "ready to hang" with a 1" long sawtooth bracket.