This is a Long-billed Dowitcher (Limnodromus scolopaceus). Although the name would make you think the length of the bill is the most important feature, there's quite a bit of overlap between Long-billed and Short-billed dowitchers. One of the best ways to separate the two species is by their calls. This one did vocalize, confirming the i.d., but I didn't record it, so we'll talk about another good character that you can see in these pictures.
In this case it's helpful to look at two particular groups of feathers. Juvenile Long-billed Dowitchers have very plainly marked tertials and greater wing coverts — they're mostly gray with pale edges. In juvenile Short-billed Dowitchers, these same feathers would be highly patterned with strong rusty internal bars or stripes. To help see the tertials and greater wing coverts, I've labeled them below:
This bird was wading in the shallows and feeding along the shoreline of Salmon Creek, probing deeply with its bill.
I like the lighting in the next image. (That's a Least Sandpiper on the left.)
Although Long-billed Dowitchers are less common than Short-billed Dowitchers in this area, this is a good time of year to find them, so keep an eye out.