Glasscock County, in West Texas, is bounded on the south by Reagan County, on the east by Sterling County, on the west by Midland County, and on the north by Howard and Martin counties. Its level prairieland is surfaced by with sandy and loam soils drained by the North Concho River, Lacy Creek, Mustang Draw, and Dewey Lake. Its area is 863 square miles, and its center is at 31° 52' north latitude and 101°30' west longitude, thirty-five miles southeast of Midland. The altitude ranges from 2,300 to 2,750 feet, and the annual rainfall is 15.81 inches. The average minimum temperature in January is 22° F; the average maximum in July is 94°. The 222-day growing season produces $19 million annually from agriculture. The chief crops are cotton, grain sorghums, and wheat; beef cattle and sheep are also important. Some 56,000 acres is irrigated. There is no manufacturing in Glasscock County, but the county produces some oil. From 1925 to 1991 county production totaled more than 192 million barrels.
Glasscock County was within the hunting area of Kickapoos and Lipan Apaches in the early nineteenth century but was not attractive to early White settlers because of its aridity. One of the United States Army's defensive posts against Indians, Fort Chadbourne, was built sixty miles east of the Glasscock county line in 1853, and during the Civil War, after Fort Chadbourne was abandoned, Fort Concho, fifty miles from the line, offered protection. The Butterfield Overland Mail route passed through the southern part of the county. Glasscock County was formed in 1887 from Tom Green County and named for George W. Glasscock, a Texas Revolution officer and Texas legislator for whom Georgetown, county seat of Williamson County, was also named. Before the establishment of Tom Green County in 1874, Glasscock County was part of the Bexar District, which was subsequently divided into thirteen counties. After the Civil War, Glasscock County was part of the Pecos Military District, and cattlemen using the Pecos Trail drove herds through the area. After its founding in 1889 Glasscock County was attached for administrative purposes first to Martin County, then to Howard County. Glasscock County was formally organized after an election was held in 1893. The 150 citizens who signed the petition for organization included a number of Mexican-American shepherds or pastores. The first White settler in what is now Glasscock County was L. S. McDowell, a sheep rancher, who moved into the area in 1883. In 1890 only 208 people lived in the county, but that year movement into the region began to be promoted by the Pecan, Colorado, and Concho Immigration Association, formed in 1890, of which Glasscock County was a member. Settlers were also encouraged to move to the area through the efforts of the Ohio Land Company, which had purchased five sections of land, drilled wells, and built houses. By 1893 three small settlements, Garden City, Dixie, and New California, had been established within 1½ miles of each other near Lacy Creek. New California was selected as the county seat because its higher ground promised more easily obtainable well water. The original settlement called Garden City was abandoned, even though at the time it had the county's post office and more homes than New California. New California was subsequently renamed Garden City. Though plans for other towns did not materialize, between 1908 and 1910 the area had another settlement boom, again the result of vigorous promotional efforts by land-development companies. By 1910, 1,143 people were living in the county.
Ranching has been the most important economic activity in the county since its earliest days. In 1890 more than 45,000 sheep and almost 4,500 cattle were counted in Glasscock County by the United States census; almost 390,000 pounds of wool was produced by county ranchers that year. Meanwhile, the census found only eighty acres of land planted in corn in 1890 and late as 1900 did not count any crop production in the county at all. The increase in the county's population between 1900 and 1910, however, mirrored a rise in the number of farms in the area during that time. In 1890 there were twenty-eight farms in Glasscock County, and the number rose to forty-nine in 1900 and to 165 by 1910. In 1900 the county had only 1,100 improved acres, but by 1910 farmers had improved 15,000 acres, with 2,200 acres devoted to corn production and 1,800 acres planted in cotton. The boom was also reflected in other county developments. In 1905 two new school districts were established in the county, adding to the two original districts established in 1893. The Garden City Gazette, a weekly paper, was published between 1905 and 1913. Another paper, Lee's Reporter, was also published for about two years during this period.
The drought of 1917–18, however, severely reduced crop production and drove away many of the early residents. In 1920 the number of improved acres had declined to 11,125, with 1,600 planted in corn and 1,055 devoted to cotton; the population of the county had dropped to 555. Ranchers also suffered because of the drought. For want of grass, cattle were driven to Big Spring for sale, and when they proved too skinny to sell they were herded back to Glasscock County. Many died en route and were butchered for their hides. Nevertheless, almost 18,000 cattle and slightly fewer than 10,000 sheep were counted in Glasscock County in 1920; by 1930 the count was 17,000 cattle and 43,000 sheep. Corn production never recovered in the years following the drought, and during the 1920s cotton emerged as Glasscock County's most important crop. Of the 11,272 improved acres reported in Glasscock County by the 1930 census, corn was grown on only ninety-two acres, while cotton was planted on almost 7,400. The 1920s also saw the beginning of oil production in Glasscock County. The oil excitement began in 1917, when S. E. J. Cox, who is also remembered for bringing the first airplane to Garden City the same year, drilled the first well on the McDowell Ranch in the north central part of the county. Cox's General Oil Company attracted investors with a free barbecue, a party surpassing any known in county history, with seventy-five cattle and fifty sheep contributing to the feast. A crowd of about 10,000 ate heartily and watched horseraces. Later it was believed that Cox had faked the oil discovery; he was convicted, with Frederick A. Cook, of related oil frauds in 1923. In 1925, however, other interests developed a productive oilfield on the McDowell Ranch. Significant oil production started in 1926, and the county briefly experienced a boom. The town of Drumright, south of the county's first producing oil well, saw its population jump to 500, but faded away as new drilling opened only dry holes. Landowners were amazed during the early years of oil fever to receive offers of $1,000 an acre for land they had bought for a dollar an acre. Despite this boom the county's development did not include large, lasting increases in population. Though the population jumped to 1,263 in 1930, by 1940 it had leveled off to 1,193, or about as many people as had lived in the county in 1910. In 1950, 1,089 people lived in Glasscock County, and by 1960 the population was 1,118. Nevertheless, after 1925 oil production gradually became one of the mainstays of the county's economy. As late as 1942 yearly production was only 10,000 barrels, but in fiscal year 1944 it totaled more than a million barrels, and in 1950, 1,296,457 barrels. By 1960, when almost 1,459,000 barrels was produced in Glasscock County, more than million barrels of oil had been pumped in the county since 1925.
The county has never had railroad service. It paved its roads first in 1936. In 1992 the county's road network included State Highway 137 and Farm Road 33 (north-south) and State Highway 158 (east-west). The population grew slowly after 1970, when 1,155 people lived in Glasscock County. By 1980, 1,200 people were counted by the census; in 2014 the population was 1,291. Of these, 64.9 percent were Anglo, 1.8 percent African American, and 32.5 percent Hispanic. Communities included Garden City (355), Lees (also known as Lee Store), and Saint Lawrence. Boating and fishing at lakes Curry and Dewey, hunting, and local events provide the county's recreation and entertainment.