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.