Middle Sister, Monument Valley. The Three Sisters are among the most noted sandstone formations in Monument Valley. The two outer Sisters had been climbed by Layton Kor and his party in the fall of 1966 and so the middle tower whetted our “first-ascent hunger.” Along with the Totem Pole, it is probably the thinnest tower in the region. Wind hampered our progress; we had to return several times to the ascent, which we finished on April 20. Pat Callis, Harvey T. Carter, Eric Bjornstad and I found the range of difficulties from F8 climbing to A3 nailing. We placed 24 pitons and on the final summit tower, 33 bolts.