Evidence of early human habitation in this area is found in Cerro de las Navajas and Zacualtipán, in the Sierra de Pachuca. Here primitive mines to extract green obsidian, arrow heads, scraping tools, and
mammoth remains can be traced back as far as 12,000 BCE. An ancient pre-Hispanic obsidian tool-making center has also been found in the small town of San Bartolo near the city. Around 2,000 BCE nomadic groups here began to be replaced by sedentary peoples who formed farming villages in an area then known as Itzcuincuitlapilco, of which the municipality of Pachuca is a part. Later artifacts from between 200 CE and 850 CE show
Teotihuacan influence with platforms and figurines found in San Bartolo and in Tlapacoya, and it has been argued Teotihuacan monopolized the Pachuca deposit to control and influence Obsidian trade in Central Mexico during the Classic Period. Development of this area as a city, however, would lag behind other places in the region such as
Tulancingo,
Tula and
Atotonilco El Grande, and there are several versions of this story. The most probable comes from a work called "Descripción Anónima de la Minas de Pachuca" (Anonymous Description of the Mines of Pachuca) written between the end of the 16th century and the beginning of the 17th. This work claims that the first mineral deposits were found by Alonso Rodríguez de Salgado on his ranch on the outskirts of Pachuca in two large hills called Magdalena and Cristóbal. Mining output had waned by the 18th century due to flooding, but was revived in 1741 by the first Count of Regla,
Pedro Romero de Terreros, and his business partner Jose Alejandro Bustamante, who invested in new drainage works. Cornish companies eventually dominated mining here until 1848, when the
Mexican–American War forced them to sell out to a Mexican company by the name of Mackintosh, Escondón, Beistegui and John Rule. Mining operations resumed in 1850, especially in the Rosario mine. Mining operations were disrupted again by the
Mexican Revolution in the early 20th century. The city was first taken by forces loyal to
Francisco I. Madero in 1911. Roberto Martinez y Martinez, a general under
Pancho Villa, entered the city in 1915. Both incursions were due to the economic importance of the mines here. During this time American investors came to Pachuca, again updating the mining technology used here. From 1906 to 1947 the United States Smelting, Refining and Mining Company was the primary producer here, with output reaching its peak in the 1930s. However, by 1947, mining here had become too costly, because of political instability, labor disputes and low prices for silver on the world market. The company sold its interests to the Mexican government in 1965. The decline in mining here in the mid-20th century had disastrous effects on the city. Many of the abandoned houses and other buildings were in danger of collapse. Under ownership of the Mexican government, mining came to a near standstill. During this time Pachuca's economy began to shift from mining to industry. The old Instituto Científico Literario Autónomo de Hidalgo was converted to the Universidad Autónoma del Estado in 1961, which would become one of the impetuses to the growth of the city in the following years, turning out as it did a better-educated and more technical workforce in areas such as law, engineering, business and medicine. In the late 1950s and through the 1960s, some growth was seen in the way of suburban developments for workers in newly built factories. Population growth returned in the 1970s and continued through the 1990s because of the growth of non-mining industries as well as a development of a large student population for the state university as well as other educational institutions. Another impetus was the movement of many government offices to Pachuca with new government facilities such as the State Government Palace and the State Supreme Court built in the 1970s. Much of the city's growth during this time was due to new housing projects, but infrastructure projects such as the new Municipal Market, the remodeling of the Plaza
Benito Juárez and the main bus station also took place. ==Geography==