INTRODUCTION. XIx 
area of similar size yet observed in the State, not excepting even the 
remarkable region of the Leadville mines. 
If one examines a general geological map of Colorado it will be noted 
that at just this poimt the strike of the Paleozoic rocks resting upon the 
Sawatch granite changes abruptly from a little west of north to northeast. 
The geological significance of this change of strike is that here is the point 
where the two converging uplifts of the Sawatch and the younger Elk 
Mountains come together, and that, whereas north of this point there was 
room for the sedimentary beds included between them to be compressed into 
broad anticlines and synclines, here they came so close together that there 
was no room for the development of more than embryonic folds, and the 
rock strata were crushed, squeezed, and broken into narrow blocks or sheets 
by a complicated system of faults. 
DISCOVERY. 
Though it is doubtful whether the early prospectors possessed a suffi- 
ciently broad geological knowledge to have observed the above facts, it is 
tolerably certain that those who first came here in 1879, men who had been 
working in Leadville, had observed on the maps of the Geological Atlas of 
Colorado that the Paleozoic rocks that carry the silver at Leadville nearly 
encircle the Sawatch uplift, and that, with the keen observation that charac- 
terizes men of their profession, they selected limestone beds of the same 
horizon as the ore-bearing zone at Leadville in which to make their 
investigations. 
In the summer of 1879 the Durant, Iron, Spar, Monarch, Late Acqui- 
sition, and Smuggler claims were located. During the winter work was 
suspended, in great measure because of the Indian revolt on the neighbor- 
ing Ute reservation. In the spring of 1880, however, the Emma, Aspen, 
Vallejo, Mollie Gibson, Argentum-Juniata, Della 8., J. C. Johnson, Park- 
Regent, and other claims were located. The town, which had at first been 
called “Ute,” was rechristened Aspen, probably from the abundance of that 
tree on the neighboring hills. Explorations continued along the strike of 
the limestone belt, and claims were located along it for a distance of 30 to 
45 miles, reaching the valley of the Frying Pan on the northeast and that 
of Taylor River on the south. Ashcroft, at the head of Castle Creek, was 
at first the most important mining town, but although the geological indica- 
tions around it are most promising, but few considerable bodies of rich ore 
