[3][4] Throughout its history, the town's population grew and declined in time with the price of silver, as the mines and the mill opened, closed, and changed hands over the years.

[3][7][8] The earliest known residents of what is now Santa Cruz County were the Apache, Yaqui and Hohokam Indians who settled on the banks of local waterways, including Harshaw Creek, in order to facilitate farming.

It was not until 1752, in response to hostilities by the Pima Indians, that Spain established its first formal settlement and military presence in Arizona at Tubac on the Santa Cruz River northwest of the site of Harshaw.

[2][3][8] After a few years of prospecting in the region, Harshaw staked claims to several deposits of silver ore, one of which he sold to the Hermosa Mining Company around 1879.

[2][3][18] In addition to digging and working what was to become the Hermosa mine, the company also began construction on a nearby twenty-stamp mill designed to process or "stamp" the silver ore into fine powder in preparation for smelting.

[4] Harshaw was soon home to some 200 buildings, 30 of them commercial, including eight or ten general stores, hotels, blacksmiths, stables, breweries, dance halls, and numerous saloons arrayed along its 3/4-mile (1.2 km) main road.

[20] Harshaw received mail service on the Southern Pacific Railroad via Tombstone three times a week,[20] and had its own newspaper, the Arizona Bullion, run by Charles D. Reppy and Company.

[2][21][22] Harshaw was dealt a devastating blow when the Hermosa mine and mill both closed down in late 1881 due to a drop in the quality of silver ore extracted from the property.

[3][8] Shortly thereafter, in 1882, The Tombstone Epitaph noted Harshaw's decline, and wrote that over 80% of the town's 200 buildings stood empty "with broken windows and open doors.

[23] The Hardshell Mine that David Harshaw discovered in 1879 and sold to R. R. Richardson began to produce silver in 1896, further spurring the town's growth.

Harshaw's rundown landscape proved to be an irritant to the Forest Service who, in 1963, tried to work with the residents to facilitate a plan to relocate the remaining families and clean up the town site.

[30] The most prominent building still standing is the James Finley House, now preserved and listed on the National Register of Historic Places as of November 19, 1974.

Of the remains, the cemeteries and the nearby adobe ruin are most easily accessible, as they are on the side of Harshaw Road, today designated as Forest Route (FR) 49.

[3][7][8][31] As of 2009, efforts are underway by the Center for Desert Archaeology to have the Santa Cruz Valley, including the remains of Harshaw, declared a National Heritage Area.

The next most common bedrock is Cretaceous andesite[35] mainly present in lava flows and tuffs in low-lying areas underlying the rhyolite and overlying the older sediments.

Andesite formations include a circular area just north of Harshaw, and a belt extending northward along Patagonia Road for about 3 miles (4.8 km).

[33] In smaller areas, the bedrock is a narrow, 3 miles (4.8 km) long strip of quartz diorite running from the southeast of Harshaw northwestward to Alum Canyon, a narrow belt of granite porphyry beneath deposits of rhyolite along the western border, and Paleozoic limestone in a small east-west belt along the middle part of the southern border of the district.

In addition, Quaternary period gravel deeply covers the underlying bedrock in two areas in the northeast and southwest borders of the district.

[33] The two silver lodes associated with the Hermosa Mine are fault breccias embedded in rhyolite dating back to the Triassic or Jurassic period.

[33] As of 2006, interest in mining the area resurfaced when the Canadian Wildcat Silver Corporation acquired an 80% share in the Hardshell property and began feasibility assessments.

[4][24][47] At its peak in the 1880s and 1890s, Harshaw's location was considered scenic as it was surrounded by oak forests, lush pastures, and enough pure mountain water to adequately run the mill and work the ore.[4][20][23] Today, Harshaw Creek is lined with sycamores, cottonwoods, and willows which are typical foliage in more arid riparian zones,[8][34] as well as enough grass to sustain limited cattle grazing.

In particular, the waste dump of the abandoned Endless Chain Mine, which is located near the headwaters of Harshaw Creek, is one of the largest contributing factors in the pollution.