The conquest of northwest Mexico had distinctive characteristics because the limits of the area known as Mesoamerica and the beginning of Aridoamerica met there. This lead to the establishment during colonial times of four types of settlements strongly interlinked: prisons, towns where the Spaniards lived, mining towns and Jesuit missions, the last provided mining towns with food supplies and other articles. During the viceroyalty, mining was the main economic activity in the northwest, therefore, the most important towns in the region originated by this trade were located on the Sierra Madre Occidental, and among them was Cosalá, founded on March 13 1562. With the settlement of the conquerors as of the XVI century, exploitation of mines located around Guadalupe de los Reyes, San José de las Bocas and Cosalá started, the last became in the XIX century the most important in this region, and in 1898 it became the most famous because it produced 50% of the silver exported by the State of Sinaloa.
Cosalá was named Royal Mines by the Spanish authorities, and it also was a trade exchange center for the rest of the mines located near by. The church seat and the military authorities were also there, together with the Assay House. Through the years, the city became very important and in 1826 it was named the capital of the Western State that included the present states of Sonora and Sinaloa in Mexico, and Arizona in the United States.
Surrounded by mountains, which are an integral part of its urban image, Cosalá has three clearly differentiated areas in its monument zone: the historical downtown area, La Canela and the Llano de Carrera neighborhoods. Because of its topography the historical downtown area consists of a totally irregular geomorphic design, the essence of which has been kept up to now, creating streets and side streets that end unexpectedly to surprise us with beautiful corners and visual ends everywhere. The value of its architecture is fundamentally provided by the characteristics it has as a whole: constructions lined to its streets, with adobe walls that end in a molding between the wall and the roof tiles provide a constant and marked homogeneity to their image; the use of materials found in the region such as beam, reed and bamboo roofs, with mud and tiles, is an evidence of how the architecture in the town is fully integrated to nature. The more than one-meter wide adobe walls, in some cases, work as thermal insulation for temperature changes. While in the historical downtown area houses are aligned to the street and have arched patios inside, at Llano de la Carrera their architecture corresponds to the typological characteristics of the rural architecture of the northwest of Mexico: constructions backed from the street alignment, with a tiled porch at the front and another one inside, and a central body that corresponds to the rooms.