Andrews County, in the southern High Plains, is bounded on the west by New Mexico, on the north by Gaines County, on the east by Martin County, and on the south by Winkler and Ector counties. The center of the county is at 32°18' north latitude and 102°50' west longitude, 110 miles southwest of Lubbock. Andrews County encompasses 1,504 square miles of level, rolling prairieland typical of the southern High Plains. Sandy soils predominate except in the east, where red clay loam is found. The elevation varies from 3,000 feet in the south to 3,400 feet in the north. The average annual rainfall is 14.37 inches, and temperatures range from a January average minimum of 30°F to a July average maximum of 96°F. The growing season is 213 days. The county's road network includes Highway 385 (north‑south), Highway 176 (west‑east), and Highway 115, which bisects the other roads at Andrews.
Angostura type arrowheads discovered by archeologists indicate the possibility of an aboriginal population as early as 6,000–4,000 B.C., but pottery sherds and other evidence establish occupation by the Anasazi people from around A.D. 900. In more recent times the Apaches and Comanches occupied the region, until the United States Army campaigns of 1874–75 cleared the way for White settlement.
The county was formed from Bexar County on August 21, 1876, a year after the first detailed explorations made by Col. William R. Shafter from his military base at Fort Concho. The county was named for Richard Andrews, a hero of the Texas Revolution who was killed at the battle of Concepción in 1835. Subsequent boundary alterations occurred in 1902, 1931, and 1932. For administrative purposes the area was placed within the jurisdiction of Shackelford County in 1876, within the Howard Land District from 1882 to 1887, and within the Martin Land District from 1887 to 1891. The area was placed within the jurisdiction of Martin County from 1891 until 1910, when Andrews County was formally organized with Andrews as its county seat.
In 1886 O. B. Holt first filed on county lands, although the huge Chicago Ranch, founded by Nelson Morris, a Chicago meat packer, purchased 228,000 acres in the southeastern corner in 1884. The county's aridity and its lack of surface streams encouraged novel rain-making experiments in 1891 by the United States Department of Agriculture. Sixty mortars charged with blasting powder and thirty kites suspending dynamite loosed their destructive forces at clouds while a number of ten-foot balloons, each holding a thousand cubic feet of oxygen and hydrogen gas were simultaneously discharged. Despite these notable bombardments no rain fell locally, although a copious precipitation to the east and south was, perhaps, a result of the experiment. After the droughts of 1886 and 1887, Nelson Morris introduced windmills to draw ground water until he had seventy-nine of the wind machines spaced on his ranch. Morris also introduced barbed wire drift fences to contain cattle.
In 1894 the Scharbauers purchased the Wells Ranch, which with Morris's C-Ranch occupied most of the eastern part of the county. A year later the Texas legislature passed the four-section law, which helped to end open-range ranching in Texas by encouraging the breakup up of great ranches for the benefit of homesteaders and small tract purchasers.
In the early 1880s the building of the Texas and Pacific Railway through Midland, Midland County, the supply point of Andrews County, gave promise of future growth. The railroad promoted immigration and had millions of acres to offer settlers. But since there was plenty of land in West Texas with better access to transportation than Andrews County, the population grew slowly; the census showed only twenty-four residents in 1890, and as late as 1900 only eighty-seven people lived in Andrews County.
By 1910, however, the population was 975, principally farmers and ranchers. Though only 70 acres of farmland had been classified as improved in the 1900 census, by 1910 the census counted 1,105 improved acres; and by 1920 the area was more than 6,000 acres. Almost 2,700 acres was planted in corn, at that time the county's most important crop. Still, actual cropland accounted for relatively little of the county's economic activity; ranching, while declining somewhat between 1910 and 1920, continued to dominate the local economy. The 2,700 acres devoted to corn production in 1920, for example, was only a small fraction of the 366,755 total productive acres in the county that year. The county had more than 53,000 cattle in 1900, and more than 54,000 in 1910.
The terrible drought of 1917–18, World War I, the great influenza epidemic of 1917–18, blizzards, and a drop in cattle prices reduced county population to 350 in 1920. It was clear by this time that much county land was not suitable for farming. Cattle ranchers bought the abandoned lands of disappointed farmers to extend their ranges. Land owned by the University of Texas, some fourteen blocks scattered around the county, accounted for 29 percent of the total acreage, and much of this was leased for grazing purposes. Nevertheless, agricultural activity did rebound during the 1920s; seventy-five farms and ranches were counted in Andrews in 1930, nearly a 32 percent increase over the figure for 1920. During this same decade cotton came to be the single largest crop raised by the farmers of the county. While the number of acres devoted to corn production fell more than 50 percent between 1920 and 1930, by 1930 almost 1,900 acres was planted with cotton. By the 1940s, sorghum had become another leading crop.
The 1920s also saw the beginning of oil production in Andrews County. On December 5, 1929, the gusher drilled in the Deep Rock Ogden No. 1 came in. The oil had been tapped at 4,345 feet and flowed in prodigious quantities. While the excitement was general in oil-industry circles and among county residents, who braced for a great boom, prosperity did not come at once. The timing of the new field could not have been worse. East Texas fields were in full production, and the 1929 crash had devastated the market. By 1931 oil was selling for as little as ten cents a barrel. Even at that price the Andrews County oil, of low gravity and heavy in sulfur, would not have sold. Investors declined to build a pipeline into the county until 1934, when J. W. Tripplehorn bought up leases, began drilling, and encouraged Humble Oil Company (later Exxon Company, U.S.A.) to lease other lands and to build a pipeline.
Though five new oilfields drilled during the 1930s continued local petroleum development, the industry did not really boom in Andrews County until the 1940s, when twenty-six new fields were discovered. Extravagant drilling efforts during this time added an entirely new dimension to life in the county, as thousands of people traveled to the area seeking jobs in the oilfields and service industries. The population of Andrews County rose from 1,277 in 1940 to more than 5,000 in 1950, and with the growth came housing problems and overcrowded conditions in Andrews, which, like the rest of the county, experienced unprecedented growth and prosperity thanks to the oil boom.
Petroleum production continued to rise in Andrews County during the 1950s, when ninety new fields were discovered. Oil income from royalties and tax dollars provided residents with many of modern services and conveniences that could not be afforded earlier, but oil production fell off in the 1960s, when only fifty-three new fields were found, and particularly in the early 1970s, when only thirteen new fields were discovered. Unemployment mounted, and county leaders called for some diversification of industry.
Water flooding of old fields and the Arab oil embargo of 1973–74 stimulated oil production again in the 1970s, and prosperity became general through the decade. In the early 1980s, livestock production accounted for roughly two‑thirds of the county’s $11 million average agricultural income. Crops of cotton, sorghums, grains, corn, and hay accounted for the rest. About 8,000 acres of land was irrigated. Oil and gas production and related services produced most of the county's income. With an income of $146,055,000 and oil production valued at $1,213,228,209 in 1982, Andrews ranked among the leading counties of the state in median annual income and in annual oil production. The oil industry was a major source of employment; by the end of 1982 the county had produced over two billion barrels of oil. About 293,000 acres of valuable county land have been owned by the state university since 1883. Andrews County’s population was 10,352 in 1970 and was estimated at 15,000 in 1982, before declining slightly to 14,338 in 1992. Most people in the county live in the town of Andrews, the county seat, which had a population of more than 11,000 in 1982, 10,678 in 1990, and 12,736 in 2014. . In the early 1990s cattle ranching continued to be the most important agricultural activity in the county, while sorghum, cotton, and corn were the most significant crops (see CORN CULTURE, COTTON CULTURE, SORGHUM CULTURE).
As of 2014, the population was 17,477. About 42.9 percent were Anglo, 53.4 percent Hispanic, and 2.1 percent African-American. Of residents age twenty-five years and older, 68 percent had completed high school, and more than 12 percent had college degrees. In the early twenty-first century oil, agriculture and manufacturing were important elements of the local economy. More than 23,230,000 barrels of oil, and 1,669,622 thousand cubic feet of gas well gas, were produced in the county in 2004; by the end of that year 2,783,911,447 barrels of petroleum had been taken from county lands since 1929. In 2002 the county had 169 farms and ranches covering 803,998 acres, 81 percent of which were devoted to pasture and 13 percent to crops. That year farmers and ranchers in the area earned $8,671,000; livestock sales accounted for $6,432,000 of the total. Beef cattle, cotton, sorghum, grains, corn, and hay were the chief agricultural products.
Communities include Andrews, McKinney Acres (population, 927), and Florey (25). Prairie Dog Town and the Oil Museum are two of the county's most popular tourist attractions.