Fallon, William O. (Le Gros, Big), mountain man (d. 1848). Fallon was the son of a St. Louis wagonmaker and became a strong, agile man of 200 pounds, a great rider who "could mount a horse on the run and pick up a sixpence from the ground while on the gallop." He was handsome, although some thought him a bully. He had early gone to the mountains for by 1826 O'Fallon's (sic) Bluff, Lincoln County, Nebraska, was named for him although his name was Fallon, not O'Fallon. He often was confused with Benjamin O'Fallon, Indian agent, and with Thomas Fallon, who accompanied Fremont. Bill Fallon may have been a free trapper in 1828 and he operated out of Fort Union at the mouth of the Yellowstone in 1829. In 1831 he was in the Rockies, reaching Green River and George Nidever found him on the Platte in 1832, traveling with him to the Rendezvous at Pierre's Hole that summer. By that time Fallon had visited Taos, attending the 1833 Rendezvous on Horse Creek and making another southerly hunt that fall, but with discouraging results. He was on Ham's Fork in 1834 but back in Missouri the following year. He was trading with the Arickaras in 1835 and alternately on the frontier and in Missouri until 1842 when he accompanied Dr. Elijah White's Oregon party as far as Fort Laramie where there was a falling out. By 1845 he was at Los Angeles, having come in with a southern party of 30 men form Taos. He participated in the bloodless Micheltorena War on the side of the Californians against the Mexican governor, then in a campaign against the Tuolumne Indians in the north when he was shot through the cheek with an arrow. He reached Sutter's Fort (New Helvetia) early in 1846 and Joe Walker met him on Calaveras Creek in February. Fallon was a leader of the Bear Flag Rebellion, having reached Sonoma in June, 1846 and was a signer of the declaration of principles of June 14; subsequently he served in Fremont's California Battalion but was back in northern California by early 1847 when he was a principal in the Fourth Relief Party to rescue Donner survivors, leaving for the Sierra April 12 and returning two weeks later with Lewis Keseberg, the only living person discovered at the camps; Fallon's diary of the expedition was published in the California Star June 5, 1847. Fallon joined Kearny's command which left Sutter's Fort June 16 and reached Fort Leavenworth August 22, again visiting the site of the Donner debacle enroute. Fallon started for California once more in early 1848. With a Scot named Guthrie he left Fort Hall, but enroute to California they were attacked by Indians and some weeks later their mutilated bodies were discovered alongside the trail.