Clay County is on U.S. highways 287 and 82 on the Red River in north Texas, ninety miles northwest of the Dallas-Fort Worth area. The center of the county is at approximately 34°48' north latitude, 98°15' west longitude, near the county seat, Henrietta. The ninety-eighth meridian, which unofficially divides the United States into east and west, runs through the eastern part of the county. The county measures forty-six miles from north to south and twenty-five miles from east to west. The total land area is about 1,150 square miles. The terrain is nearly level to gently sloping. About a third of the county is prime farmland. The flora of most of the county is typical of the Cross Timbers and prairie, with grasses predominating. The northwest corner is in the Rolling Plains vegetation area, with taller grasses, mesquite, and cacti common. Trees, including mesquite, blackjack, post oak, and elm, are scattered throughout the county, but are more numerous along the streams. The elevation varies from 1,100 feet in the southwest to 900 feet in the east. The average rainfall is thirty inches a year. The average annual temperature is 64° F. Temperatures in January range from an average low of 28° F to an average high of 53° and in July from 73° to 98°. The growing season averages 229 days a year, with the last freeze in late March and the first freeze in mid-November. Snowfall averages six inches a year.
Clay County has many streams. The northern edge of the county is formed by the Red River; the Wichita River flows through the center of the county before dividing into two forks and emptying into the Red River. Other major streams include Turkey, Dry Fork, Hay, and East Post Oak creeks. Lake Arrowhead, in the western section of the county, is nine miles long and two miles wide and is used both as a source of water and for recreation. The fauna of Clay County is typical of North Texas, where deer, bobwhite quail, and migratory game birds provide excellent hunting. Mineral deposits in the county include building stone and clays for brick, tile, and ceramics. Oil was discovered near the site of present-day Petrolia in 1901 and has been an important asset to the county's economy, although production declined toward the end of twentieth century.
The Clay County area has long been the site of human habitation. Its earliest inhabitants were probably Archaic Age hunter-gatherers. Wichita and Taovaya Indians migrated into the area from what is now Kansas and Nebraska beginning in the middle of the eighteenth century. Despite their use of horses, which were introduced into the region by Spanish explorers, and their consequent facility as buffalo hunters, these peoples were heavily dependent on agriculture. The location of their lands placed them in conflict with the Lipan Apaches and Comanches, both of whom claimed the area and continued to visit it after they were removed to Oklahoma. The Indians often came into conflict with White settlers in the region after 1850, when federal troops forced them to move to reservations north of the Red River.
The earliest Europeans to visit the future county were Spanish explorers. Several early expeditions crossed Clay County, probably skirting the Cross Timbers. In 1759 Diego Ortiz Parrilla traveled through on his way to attack the Taovayas at the site of present Spanish Fort in Montague County, and in 1786 and 1787 Pedro Vial and José Mares traversed the area while exploring possible routes from San Antonio to Santa Fe. In July 1841 the Texan Santa Fe expedition crossed the future county heading west. The Snively expedition of 1843 cut across the northeast corner, and the California Trail cut across the southern section after 1849. In 1858, on an expedition to Oklahoma to punish the Comanches, Earl Van Dorn followed an arc-shaped route through western Clay County as he traveled from Cottonwood Spring in Young County to what became known as the Van Dorn Crossing on the Little Wichita River; the expedition detoured eastward to join the California Trail at Brushy Mound.
The first settlers in the area were probably W. T. and Wess Waybourne, who came in the 1850s and built their homes on the south fork of the Wichita River two miles from the site of present-day Henrietta. Clay County was marked off from Cooke County on December 24, 1857, and named for Kentucky statesman Henry Clay; the population of the new county was only 109 in 1860. On the eve of the Civil War, Henrietta, the largest community, had ten homes and a general store. Indians, however, remained a constant threat at this time, and the army conducted regular patrols of the area. The county was organized in 1861, but it was largely abandoned the following year because of the removal of federal troops during the war. The 1870 census gave no population figures for Clay County, although a few ranchers and farmers remained near the Red River after most of the settlers had moved eastward to more populated regions.
With the establishment of Fort Sill in Indian Territory after the Civil War, settlers began to return to Clay County. Among the first permanent residents after the war was Henry A. Whaley, who raised grain and vegetables on his farm near the mouth of the Wichita River to sell to the army at Fort Sill. The county was reorganized on May 27, 1873, with Cambridge as the county seat, and during the 1870s a small but growing stream of new settlers moved in, attracted by good range and farm land. Most of the early settlers raised cattle, along with small crops of corn and cotton. In 1882 the Fort Worth and Denver Railway was built across the county through Henrietta. The town, which had been largely abandoned since the outbreak of the Civil War, bustled with new activity; after most of the residents of Cambridge moved there because of the railroad, Henrietta was incorporated and made the new county seat.
The railroad ushered in a boom. The population grew from a few hundred in 1870 to 5,045 by 1880. Buffalo hunters returning from the West shipped their hides from Henrietta, and the city became the principal trading center with nearby Fort Sill. In 1880 the county's 635 farms produced 1,155 bales of cotton and 92,766 bushels of corn; cattle numbered 58,763. Over the next twenty years cotton production grew to 3,774 bales, corn yields increased to 721,020 bushels, and the number of cattle rose to 91,212. Between 1890 and 1910 the population grew from 7,503 to 17,043. This surge was aided by the construction of two new railroads: the Gainesville, Henrietta and Western, a branch line of the Missouri, Kansas and Texas, which reached Henrietta in 1887; and the Wichita Valley Railway, which was constructed to Byers in 1904.
With the growth in population also came a marked increase in the county's farming economy. The number of farms grew from 766 in 1890 to 2,306 in 1910, and the number of acres under cultivation nearly tripled. At the turn of the century Clay County was primarily composed of ranches and farms, with the majority of its population living in rural areas. Before 1900 the leading crop was corn, but increasingly during the early years of the new century cotton took center stage. In 1890, 6,135 acres had been planted in cotton; by 1910 that figure had grown to 71,086; and by 1930 nearly one of every two improved acres-more than 80,000 in all-was given over to cotton production.
Cotton culture brought prosperity, but it had disastrous effects during the Great Depression. Many farmers borrowed heavily against future crops, encouraged by the unprecedented income earned by cotton in the 1920s. Moreover, about half of the farmers in Clay County in 1930 were tenant-sharecroppers who worked someone else's land for a share of the harvest. With the drop in cotton prices during the depression and the ensuing credit crunch, many farmers found it impossible to get by and were forced to give up farming permanently. Between 1930 and 1940 the number of farms in the county fell from 2,106 to 1,710, and over the next ten years the number dropped again by nearly a half. Hardest hit were the sharecroppers, who had little in the way of cash or assets to help them over tough times. Between 1930 and 1940 almost half of them were forced off the land, and within two decades virtually none of the tenants remained. The depression years permanently changed the face of the county's farming economy in other ways as well. After World War II cotton farming gradually gave way to cattle ranching, and by the late 1960s fully three-fifths of farm income came from livestock, principally beef cattle.
Between the 1920s and the 1980s the county population declined slowly, from 16,864 in 1920 to 14,545 in 1930, 12,524 in 1940, 9,866 in 1950, 8,351 in 1960, and 8,079 in 1970. During the late twentieth century the population grew slightly, increasing to 9,582 in 1980 and 10,024 in 1990, largely as the result of increasing emphasis on manufacturing. Unemployment was only 1.1 percent in 1986, and, although the jobless rate climbed in subsequent years, it remained well below the statewide average; in 2000 only 2.1 percent of the workforce was unemployed. In 1986 more than 82 percent of Clay County residents owned their homes. The average family weekly income of $335.45, however, remained lower than that of many other areas of the state. Many new jobs came from light manufacturing, introduced into the area in the 1970s and 1980s. As late as 1965, 181 people were employed in oil and gas operations and 241 worked in retail business, but in the early 1990s only a handful of oil workers remained. Mobile-home and wood-products plants, established during the 1970s and 1980s, added 189 jobs to the county's rolls and helped to offset losses in other areas.
Like most Texas counties, Clay County made significant improvements in education in the late twentieth century. In 1950 only 23.5 percent of adults twenty-five and older had a high school education, and only 4 percent had a college degree. In 1980, 50 percent of adults twenty-five and over had high school diplomas, and 7 percent had college degrees. In 1990 Clay County was divided into five school districts. White students constituted 97 percent of the student body, 2 percent were Hispanic, and Black students .5 percent.
Politically, Clay County has been staunchly Democratic throughout most of its history. A majority of the county's voters voted for Democratic presidential candidates in virtually every election from 1876 through 1968; the only exception was 1928, when Republican Herbert Hoover beat Democrat Al Smith. The county's voters gradually began to trend somewhat more Republican after 1972, when Republican Richard Nixon took the county, though the Democrats remained strong there until very late in the twentieth century. Democratic candidates carried the county in 1976, 1980, and 1988, and Democratic presidential candidate Bill Clinton carried the county by a plurality in 1992 (partly because third-party candidate Ross Perot got about 28 percent of the county's votes that year). Republican candidate Bob Dole won a plurality there in 1996, however, when Perot got only about 11 percent, and Republican George W. Bush won majorities in the county during the 2000 and 2004 elections.
In 2014 the census counted 10,370 people living in Clay County. About 91 percent were Anglo, 5.2 percent were Hispanic, and 1 percent were African American. By 2000 more than 80 percent of residents age twenty-five and older had graduated from high school, and almost 14 percent had college degrees. In the early twenty-first century the county's economy continued to center on ranching, farming, oil, and manufacturing. In 2002 the county had 892 farms and ranches covering 654,342 acres, 68 percent of which were devoted to pasture and 28 percent to crops. In that year farmers and ranchers in the area earned $39,164,000; livestock sales accounted for $35,239,000 of the total. Beef and dairy cattle, horses, wheat, cotton, pecans, and peaches were the chief agricultural products. More than 742,000 barrels of oil and 258,589 cubic feet of gas-well gas were produced in the county in 2004; by the end of that year 204,088,003 barrels of oil had been taken from county lands since 1917.
Henrietta (population, 3,175) is the county's largest community and its seat of government. Other towns include Petrolia (675), Byers (481), Bellevue (360), Dean (498), and Jolly (184). Local attractions include hunting and fishing, Lake Arrowhead State Recreation Area, and the Pioneer Reunion Festival and Junior Stock Show, both held annually in Henrietta.