Upton County is in southwestern Texas. The center of the county lies at 31°22' north latitude and 102°02' west longitude. Rankin, the county's seat of government, is fifty air miles south of Midland. The area was named for Confederate generals John C. Upton and William F. Upton. Upton County covers 1,241 square miles of rocky land in the Edwards Plateau vegetation region; elevations range from 2,300 to 3,000 feet above sea level. While northern sections of the county are flat, the southern sections are rolling and hilly and are pierced by numerous small lakes. The county's exposed limestone surfaces and sandy loam soils are covered with scrub mesquite, greasewood, cacti, catclaw, and grasses. King Mountain in the southwest is the area's highest point; Castle Mountain is fifteen miles north and Moltke Hill is fifteen miles southeast of King Mountain. Numerous small lakes drain to the tributaries of the Middle Concho and Pecos rivers. Rainfall averages only 12.70 inches annually. Temperatures range from an average minimum of 33° F in January to an average maximum of 96° in July. The average growing season lasts 232 days. Mineral resources include caliche and limestone. The area's transportation network includes U.S. Highway 385, U.S. Highway 67, and State highways 329 and 349.
The area that is now Upton County was traversed during the early nineteenth century by Comanches and Apaches, who competed for hunting grounds in the area. Both tribes were superior horsemen, capable hunters of buffalo and other game, and relentless raiders of their neighbors. Despite their considerable achievements in material culture and adaptation to their environment, the Indians lost their domination of the region to the United States Army and the advancing tide of white settlers in the 1870s and 1880s. In the 1860s the Chihuahua Trail from Mexico to Indianola, Texas, a significant trading route, crossed the region, as did the route of the Butterfield Overland Mail (1858–61), and the Goodnight-Loving Trail. Originally part of the Bexar Territory, the area was part of Tom Green County from 1874 until 1887, when Upton County was established. One of the earliest settlers was Dr. George W. Elliott, who moved into the area in 1881 and drilled the first well; he reached water at thirty feet. The area was part of the open range until the 1890s, when sheepmen crossed the Pecos River to compete with cattlemen for the range. The United States Census counted fifty-two people living in the county in 1890, and only forty-eight in 1900; most of these belonged to the families of Arthur F. Schnaubert, Frank Inghram, and Jim O'Bryan, or were hired cowboys and ranch hands. According to the agricultural census for 1900, there were eighteen ranches that year; almost 39,000 cattle were reported, but virtually no crops were grown. The area began to attract more settlers in the early twentieth century. In 1900 and 1901 open range cattlemen started selling their holdings, and the state encouraged the sale of school and railroad lands for settlement. Rancher Henry M. Halff tried to develop an irrigation area for cotton and vegetable raising and sold town lots at Upland for the price of a notary fee. Upland opened a public school in 1908. By 1910 there were 105 ranches or farms in the area, and the population had increased to 501; the county was organized that year, and Upland became the county seat.
In the fall of 1911 the Kansas City, Mexico and Orient Railway reached the townsite of Rankin, and by January 1912 most of the people living in Upland had moved to Rankin. The county's population soon was concentrated at or near Rankin, and after 1913 the town's school system served the entire county. Rankin became the county seat in 1921. Between 1911 and 1912 some farmers, discouraged by poor soil and droughts, abandoned their efforts to raise crops in the area. Remaining settlers who raised horses, cattle, and sheep did well during the high market price years of World War I, but by 1920 only thirty-one ranches or farms remained, and only 253 people lived there. Events soon demonstrated that the county's economic future was tied to oil. In 1926 George McCamey's wildcat brought 700 hopeful people to the area and established a new town in the southwest corner of Upton County named for the oil discoverer. The opening of the Yates oilfield especially helped to develop Upton County's economy. The Yates field actually lies in Crockett and Pecos counties, but Rankin developed as the supply and oil service center for the rich district and boomed as a result. Yates No. 1-A was brought in on October 28, 1926, flowing at 450 barrels daily, and later Yates No. 30-A became the largest gusher in the world, with a flow of 200,000 barrels a day. McCamey field operators gained a railroad spur from the Santa Fe Railroad, which had taken over the Orient Railroad, to aid development and encourage growth of the new town. By late 1927 several thousand people lived in McCamey. Water had to be freighted from Alpine, 100 miles distant, and was sold at one dollar per barrel until 1929, when good water from the Trinity sands wells seventeen miles away was piped into the town. Meanwhile the agricultural sector of the county developed slowly, and in 1930 there were thirty-six ranches or farms in the area. The number of cattle had declined to 17,819 by that year, and only two acres of crops were harvested in the entire county. Nevertheless, largely because of oilfield activity, the population grew dramatically during the 1920s, and by 1930 there were 5,968 people living there. Oil activity declined during the early 1930s after the East Texas oilfield opened in 1931–32 and the Great Depression drove oil prices down. Nevertheless in 1938 almost 5,575,000 barrels of crude were produced. Sheep ranching revived in the late 1930s, and cattle ranching continued to decline; in 1940 almost 120,000 sheep and 8,500 cattle were reported in the county. The population declined to 4,297 by 1940.
Oil production accelerated again in the 1940s after the beginning of World War II; in 1944 almost 7,859,000 barrels were produced. Development of the area's oil continued after the war. Benedum field, in the northwestern part of the county, was discovered in 1947; by 1954 1,800 wells had been drilled in the area, and Plymouth Oil Company, Phillips Petroleum, Texas Natural Gas, and El Paso Natural Gas Company had established large plants and pipelines to carry oil, gas, butane, propane, and butadiene from their plants and the field to all parts of the country. More than 7,996,000 barrels of crude were produced in 1948, more than 15,431,000 barrels in 1956, almost 12,815,000 barrels in 1960, and more than 18,426,000 barrels in 1965. Meanwhile, McCamey's water system was expanded in the 1940s and 1960s, and with water resources the town pushed forward to become both the power and light plant center and the oil well supply center for a large part of West Texas. The county's population rose to 5,307 by 1950 and to 6,239 by 1960. Oil production had begun to decline by the early 1970s and continued to drop into the early 1990s. About 13,106,000 barrels were produced in 1974, 11,164,000 barrels in 1982, and 9,398,000 barrels in 1990. By January 1, 1991, almost 678,715,000 barrels of crude had been taken from county lands since 1925. In 1982 about 92 percent of the land in Upton County was in farms in ranches, but less than 1 percent of the county was considered prime farmland, and only 2 percent of the county was cultivated. About 56 percent of the county's agricultural income was derived from crops, especially cotton, wheat, and alfalfa; watermelons and pecans were also grown. Livestock, especially cattle and sheep, were also important to the local economy. The population dropped to 4,697 by 1970, to 4,619 by 1980, and to 4,447 by 1990. The voters of Upton County supported the Democratic candidates in virtually every presidential election from 1912 to 1948; the only exception occurred in 1928. The county's electorate voted Republican in almost every election between 1952 and 1992, except in 1960 and 1964. As of 2014, 3,454 people lived in the county. About 44.5 percent were Anglo, 2.6 percent African American, and 51.6 percent Hispanic. Major communities include Rankin (population, 754), the county seat; McCamey (1,860); and Midkiff (182). Rattlesnake roundups at Rattlesnake Butte and rattlesnake races at McCamey have been annual events since 1936. McCamey is also home to the Mendoza Trail Museum. Rankin hosts the County Livestock Show in January, a Junior Rodeo in June, and a Christmas Parade in December.