Ruby Mountain is a prominent North Cascades summit in Washington, rising sharply above Diablo Lake near the meeting of Ruby Creek and the Skagit River. Its steep relief, with the summit climbing about 6,200 feet in roughly two miles, and its split drainage toward Ross Lake and Diablo Lake reflect the rugged terrain of the range. The mountain was named for Ruby Creek, which local tradition ties to an 1872 journey by John Sutter, George Sanger, and John Rowley, when Sutter reportedly found a ruby. Its first recorded ascent came in 1916 by forest ranger Tommy Thompson. Ruby Mountain also bears the marks of tectonic uplift and repeated Pleistocene glaciation.