A glacier-and-rock climb up Boston Peak from the same Boston Basin camp used for Sahale Peak, Sharkfin Tower and Forbidden Peak, finished on an exposed, loose ridge.
Approach as for Forbidden Peak and Sahale Peak: register in Marblemount, drive to the Boston Basin Trailhead, and hike the steep climbers' trail up the old mine road and into Boston Basin, camping around 6,200-6,400 feet. From camp, head toward the left (north) side of Sharkfin Tower and rope up for glacier travel around 6,700 feet. Make a rising traverse near the cliffs below Sharkfin to reach a flatter section of the Quien Sabe Glacier, then pick a line up its steeper upper section, avoiding crevasses. Later in the season it is usually easiest to traverse right to end-run the bergschrund before cutting back up and left to the Boston-Sahale col. Unrope at the col and follow the ridge toward Boston Peak. The ridge starts flat, then widens onto loose rock before steepening and narrowing to an exposed, knife-edge section. A short double-rope rappel from the ridge gains a col to the west, from which the final short scramble reaches the summit.
Reverse the ridge and glacier to Boston Basin camp; established rappel anchors are generally present on the rock walls along the ridge for the section that was rappelled on the way up.