Location
North end of the Gila Mountains; south bank of the Gila River, T. 8 S., R. 21 W.
Topographic Maps
Laguna Dam and Dome 7 1/2-minute quadrangles; Laguna 15-minute quadrangle.
Geologic Map
Wilson, 1960, Geologic Map of Yuma County, Arizona, scale 1:375,000.
Access
From Yuma, about 13 miles east on State Highwav 95 to Blaisdell; light-duty road parallels the Southern Pacific 7 miles east to Dome.
Extent
The Gila City placers occur on the narrow gravel-mantled pediment at the north end of the Gila Mountains formed on a bedrock of Tertiary sedimentary rocks that are faulted against the schist of the main mountain mass. Gold has been found in gulch and bench gravels of Quaternary age that mantle the Tertiary sediments to depths of 15 feet.
The area of gold-bearing gravel extends from 1/4 mile east of Dome to 3 miles west of Dome, but most placer mining is centered around Monitor Gulch, 1 1/2 miles west of Dome (sec. 11, T. 8 S., R. 21 W., Laguna Dam quadrangle). Most of the gold in the gravels was found at or near bedrock in gulches, but much gold was recovered from bench gravels in the area. Gravels more than 15 feet above bedrock have not been profitable.
Production History
The Gila City placers were discovered in September 1858 by Colonel Jacob Snively and were actively worked by hundreds to thousands of men until about 1865, when the richest gravels were depleted. Gila City, a placer boom town that lived only 4 years, was near the mouth of Monitor Gulch adjacent to the Southern Pacific (NW 1/4 sec. 11, T. 8 S., R. 21 W.).
Lieutenant Sylvester Mowry, a noted Arizona miner and pioneer, visited the placers in November 1858 and reported that men were recovering $30 to $215 per day; he witnessed $20 in gold washed from eight shovelfuls of dirt by an unexperienced placer miner.
After the initial boom period, mining continued in the district on a much reduced scale; all the known productive ground is said to have been worked over at least once. Most of the gold was recovered by first drywashing, then by wetwashing the dry-panned concentrates at the Gila River. A few large-scale operations have been attempted, but these were unsuccessful.
Source
Wilson (1933, p. 210) states that the gold in the Gila City placers probably came from many pockety or small low-grade gold veins in the northern end of the Gila Mountains. No high-grade gold veins are found in the vicinity of the placers.
Literature
Browne, 1868: History of placer-mining activity.
Elliott, 1884: History—quotes Lieutenant Mowry's description ol placers; placer-mining activity and production in 1858.
Farish, 1915a, v. 1: Repeats Lieutenant Mowry's description of placers.
Hinton, 1878: History of early placer-mining; quotes Browne's (1868) description of early history of Gila City.
Koschmann and Bergendahl, 1968: History; production.
Mowry, 1863: Early placer-mining activity.
Raymond, 1872: Extent; placer-mining operations.
1874: Production information for 1873.
Trippel, 1889: Production statistics for 1888.
Wilson, 1933: History; location; production; bedrock geology; character of gravels; area of placer-mining activity; source of gold. 1961: Virtually repeats Wilson (1933).
