The Tetons received their name from French-Canadian trappers who accompanied the earliest British expeditions into this territory. As they approached the range from the west, they beheld three towering mountains upon which they bestowed the name of “Trois Tetons” (“Three Breasts”). This romantic designation was readily adopted by the lonely trapping fraternity to whom the sharp snowy peaks (now known as the Grand, Middle and South Tetons) became a beacon to guide them through the hostile wilderness. To the Indians the Tetons were variously known as “The Three Brothers,” “The Hoaryheaded Fathers,” and “Tee Win-at,” meaning “The Pinnacles.” The earliest Americans in the region, being more practical than romantic, could find no better name for the silvery spires than “The Pilot Knobs,” while an official Hudson’s Bay Company map indicates with equal homeliness, “The Three Paps.” The name “Three Tetons” survived, however, and was officially recognized by cartographers. The name first appeared publicly in the Bonneville Map of 1837. The Upper Snake River (i.e., above the mouth of Henry’s Fork) was called “Mad River” by the Astorians. Others simply referred to it as the “Columbia River” or “the headwaters of the Columbia,” but to most of the fur trappers it was “Lewis River” or “Lewis Fork,” so originally named in the Clark Map of 1810 for Capt. Meriwether Lewis, as Clark’s Fork of the Columbia was named after his fellow explorer, Capt. William Clark. This name was much more appropriate than its present one, which is derived from the Snake or Shoshone Indians, and first appears on the Greenhow Map of 1840. In spite of past efforts by water power advocates to “improve” it by a dam, Yellowstone Lake remains just as it was when first discovered by John Colter, the original “Lake Eustis” of the Clark Map of 1810. Jackson Lake, however, was enlarged by a dam built in 1916 by the Bureau of Reclamation. This lake is identifiable with the “Lake Biddle” of the Clark Map of 1810, the “Teton Lake” of Warren A. Ferris, and the “Lewis Lake” referred to frequently by another trapper, Joseph L. Meek. There is today a tributary of the Upper Snake known as Lewis River, heading in a Lewis Lake within the confines of Yellowstone National Park, neither of which are to be confused with the historic “Lewis River” and “Lewis Lake.” [Illustration: Grand Canyon of the Yellowstone.] [Illustration: POWDER HORN] II. The Mystery of “La Roche Jaune” or Yellow Rock River