Hugo O'Conor, the founding father of the city of Tucson, Arizona authorized the construction of a military fort in that location, Presidio San Agustín del Tucsón, on August 20, 1775 (near the present downtown Pima County Courthouse).During the Spanish period of the presidio, attacks such as the Second Battle of Tucson were repeatedly mounted by Apaches.Over the following years, the city continued to grow, with the population increasing to 20,292 in 1920 and 36,818 in 1940.In 2006, the population of Pima County, in which Tucson is located, passed one million, while the City of Tucson's population was 535,000.
Brazelton held up two stages in the summer of 1878 near Point of Mountain Station approximately 17 mi (27 km) northwest of Tucson. to send special agent and future Pima County sheriff Bob Paul to investigate.
Arizona, south of the Gila River, was obtained via treaty from Mexico in the Gadsden Purchase on June 8, 1854.
Tucson became a part of the United States of America, although the American military did not formally take over control until March 1856.
In 1885, the University of Arizona was founded as a land-grant college on over-grazed ranch land between Tucson and Fort Lowell. Veterans Administration had begun construction on the present Veterans Hospital.
In 1890, Asians made up 4.2% of the city's population. The population increased gradually to 13,913 in 1910. Many veterans who had been gassed in World War I, and were in need of respiratory therapy, began coming to Tucson after the war, because of the clean dry air.
From August 1861 to mid-1862, Tucson was the western capital of the Confederate Arizona Territory, the eastern capital being Mesilla.