Sedge Creek—K: 11—1885—U. S. G. S.—Characteristic.
Senecio Creek—S: 13—1885—U. S. G. S.—Characteristic.
Sentinel Creek—J: 4—1872—U. S. G. S.—“The two central ones [geyser mounds] are the highest, and appear so much as if they were guarding the Upper Valley, that this stream was called Sentinel Branch.” Bradley.
Shallow Creek—F: 11—1895—U. S. G. S.—Characteristic.
Sickle Creek—Q: 10—1885—U. S. G. S.—Characteristic.
Slough Creek—D: 10—1867—See “[Crevice Creek].”
Snake River (6,808)—W: 8—1805—Lewis and Clark—From the Snake or Shoshone Indians, who dwelt in its valley.
Soda Butte Creek—E: 12—Probably named by miners prior to 1870. From an extinct geyser or hot spring cone near the mouth of the stream.
Solfatara Creek—G: 6—1885—U. S. G. S.—Characteristic.
Solution Creek—M: 8—1885—U. S. G. S.—The outlet of Riddle Lake.