174 GUIDEBOOK OF THE WESTERN UNITED STATES 
up to the foot of the mountains, which rise abruptly with steep rocky 
slopes. To the east the rugged ridges of the Chiricahua Mountains 
are visible; 25 miles due north are the Swisshelm Mountains, which 
consist largely of Paleozoic rocks; and to the west are the Mule 
Mountains, which rise more than 3,000 feet above the valley and in 
which the great copper mining center of Bisbee is situated. To the 
south in Mexico are many high mountains and peaks, mostly of 
voleanic rock. One conspicuous conical peak to the southeast on the 
international boundary is the place where the notorious outlaw Pancho 
Villa assembled his forces before attacking Agua Prieta in 1915 
Douglas is on highway 80, which continues west through Bisbee and 
Tombstone. The city extends south to the international boundary 
and the small town of Agua Prieta, Mexico (population 2,500), with 
which it shares an international airport. Douglas, which ranks third 
in population in Arizona, is a port of entry from northern Sonora, 
Mexico, with extensive imports. Railroads branch here to Nacozari, 
in Sonora, where there are large copper mines, and northward up 
Sulphur Spring Valley to the mining towns of Gleeson, Courtland, and 
Pearce to join the north line of the railroad at Cochise, 59 miles away. 
The mines about Gleeson and Courtland are on the east slope of the 
Dragoon Mountains, in the Turquoise district, so called because 
turquoise was obtained from the quartzite and granite, mainly by 
the Indians, who greatly value the blue-green mineral as a medicine 
stone. The mines, which have been worked to moderate extent 
since 1883, have produced considerable gold, silver, lead, and copper, 
and the value of the copper output is more than $8,000,000. 
Douglas was named for Dr. James Douglas, who had much to do 
with the development of the copper industry of the Bisbee district, 
and it had the advantage of being planned as a city with the definite 
object of being a smelter and trade headquarters. It began in 1900. 
The water supply is obtained from wells 3 miles distant. 
On leaving Douglas the smelters are passed (south of the railroad), 
with their huge piles of black slag resulting from the copper smelting. 
According to the United States Bureau of Mines, in 1928 these 
smelters had a joint output of 271,400,000 pounds of copper, 5,970,118 
ounces of silver, 105,641 ounces of gold, and 14,500,000 pounds of 
lead, the largest copper-smelting output at any one place in the West. 
About 1,500 men are employed, many of whom live in the suburb of 
Pirtleville. In a short distance the railroad crosses Whitewater Draw 
*The rocks exposed in this vicinity 
comprise the Pinal schist (Archean), 
Bolsa quartzite and Abrigo limestone 
(Cambrian), limestone of Carboniferous 
~~: age, San Cretaceous age, and | were fo ‘inci ) 
_ Porphyries, granite, and Sicaius of | of the Cia eee 
_ post-Carboniferous age. The rocks are | ue 
flexed and faulted and also displaced 
by a remarkable overthrust by which 
schist and Cambrian strata are carried 
