In 1903, James Wickersham recorded the first attempt at climbing Denali, which was unsuccessful. In 1906, Frederick Cook claimed the first ascent, but this ascent is unverified and its legitimacy questioned. The first verifiable ascent to Denali's summit was achieved on June 7, 1913, by climbers Hudson Stuck, Harry Karstens, Walter Harper, and Robert Tatum, who went by the South Summit. In 1951, Bradford Washburn pioneered the West Buttress route, considered to be the safest and easiest route, and therefore the most popular currently in use.