Just east of Seattle, along the I-90 corridor, lies a mythic training ground for hikers, scramblers, mountaineers, and alpinists, lying within the recently established Mountains to Sound Greenway National Heritage Area. Peaks line the highway on either side, requiring grueling 4,000' climbs before providing incredible views of Mt Rainier (to the south) and the Central Cascades (to the north). In particular, the peaks north of the I-90 are often climbed, but none more than Mailbox Peak.
From the summit of Mailbox, views abound in all directions, but the masochist's eye will be drawn to the east - to the continuous ridge that leads (with some small interruptions) all the way to Granite Mountain, eight miles (as the crow flies) to the east. This ridgeline is relatively rarely traversed, and offers an incredible alpine adventure less than an hour from Seattle, especially if you choose to do it with snow on the ground.
This route begins at the Mailbox Peak trailhead and links together 11 summits via some gnarly schwacking, aesthetic ridge scrambling, and brief sections of trail before depositing you at the Granite Mountain Trailhead. Since much of the linkup is off-trail, the route isn't too prescriptive, and simply requires that you start and end at the proper trailheads and summit all 11 peaks, west to east, in a single push. Choose your own path based on conditions and ability.
The peaks (in west to east order):
1) Mailbox Peak
2) Dirtybox Peak
3) Dirty Harry's Peak
4) Web Mountain
5) Putrid Pete's Peak
6) Mount Defiance
7) Bandera Mountain - West Peak
8) Bandera Mountain
9) Pratt Mountain
10) West Granite (aka Tusk O'Granite)
11) Granite Mountain
There's plenty of beta on the different sections of this route, so I'm not going to write much here, but I'll warn you that the Mailbox to Dirty Harry traverse is the technical and route-finding crux of the route. Do your research. Once you're on Dirty Harry, the rest is pretty straightforward.
Credit: I know I'm nowhere near the first person to do this linkup, but I was encouraged by a few folks in the community to post this route, so I did. I first found out about the route from Yellowleaf's much more impressive "Two Box Traverse", in which he traversed from Mailbox to Hibox over 5 days, covering 48 miles and 25,000' of gain. Read more about their incredible adventure here.