Mount Washington is the central plug (volcanic neck) of an extinct shield volcano. Details of the mountains origin, eruptive history, geology, and geomorphology can be found at this USGS Mount Washington page
The mountain is located in the Mount Washington Wilderness of the Willamette National Forest. The main access to its slopes is via the Pacific Crest Trail.
Because of its beauty, easy access, and relatively simple summit route, Mount Washington is a very popular destination and the normal route can be crowded, especially on weekends.
Summit views are excellent with Mt. Jefferson and Three Fingered Jack to the north and the Sisters complex to the southeast.
The first ascent was made via a north ridge variation in 1923 by Armin Furrer, Leo Harryman, Ervin McNeal, Phil Philbrook, Ron Sellers, and Wilbur Watkins. The original ascent route no longer exists due to rock fall.
The rock on Mount Washington has a reputation for being extremely poor. Jeff Smoot describes only the North Ridge route in his CLIMBING THE CASCADE VOCANOES guide stating that most people probably would not want to climb any of the other routes anyway due to the poor rock.
All routes on the mountain are Class 5 with the North Ridge being the easiest. The ridge is wide and several variations are possible ranging from about 5.0 to 5.3.
Andy Traylor posted an FKT route:
I started from the permit box at the Big Lake Youth Camp trail. There are several other points to start this run/climb from, but this is the closest you can get by car, resulting in a round trip distance of about 8.5 miles. Perhaps the junction of this trail with the PCT would be a more appropriate starting point for the segment, and I'm certainly open to measuring from there if/when more people become interested in this peak.
There will undoubtedly be some variation in trails to the summit but I tried to take the most obvious trail, defaulting to the ridge when possible. I brought a 8mm 40m rope and a light harness to rap the first "pitch" but soloed up and down the rest of the summit spire.
Admin note: According to Emily Keddie this route is currently defunct. Therefore, the primary route should be from the PCT TH on Old Santiam Wagon Rd. From there go ~ 3 miles on the PCT and turn up the climbers' trail.