Denton County covers 911 square miles in north central Texas. Its center point is at 33°12' north latitude and 97°13' west longitude. It borders Dallas and Tarrant counties on the south and Cooke and Grayson counties on the north; it is one county south of Oklahoma. The western half of the county is surfaced by the black soil of the Grand Prairie. An eastern sliver is on the western edge of the Blackland Prairie, where the rich black soil contrasts sharply with the sandy land of the Eastern Cross Timbers jutting down from Oklahoma through the central part of the county. Denton County ranges in elevation from 500 to 900 feet, has an annual average rainfall of about thirty-three inches, and a temperature average ranging from a minimum of 34° F in January to a maximum of 96° in July. With an average growing season of 226 days, it is a good area for general crop and livestock production. The Elm Fork of the Trinity River flows through the east central part of the county. It was dammed in the 1920s to form Lake Dallas, which has since been joined with Garza–Little Elm Reservoir to form Lewisville Lake, a moderately large reservoir. The western part of the county is cut by several major creeks. Clear Creek drains into the Elm Fork and Hickory Creek into Lewisville Lake. Denton Creek and its tributaries, in the southern part of the county, are sources of water for Grapevine Lake, which is partly in Denton County and partly in Tarrant County. In the Cross Timbers and the floodplains of the creeks black jack and post oak, pecan, white ash, sycamore, cottonwood, hackberry, elm, and willow trees predominate. Most of the rest of the county was originally covered by grasses. Some native pasture remained in the 1980s, but the bulk of county land not in cultivation was improved pasture, planted mainly with coastal Bermuda grass. The Trinity Sands underlie the area at about 700 to 1,200 feet, but in some parts of the county residents are able to reach artesian water at depths as shallow as 100 feet. Though Denton County is not abundant in natural resources, it has produced a modest but significant amount of oil (5,696,311 barrels by the end of 2004), mostly from the Bolivar field between the 1930s and the 1960s. Other natural resources are natural gas, sand and gravel, and some building stone—the stone courthouse on the square in Denton was built in 1896 from stone quarried a few miles north.
Although archeological field surveys done under contract with the United States Army Corps of Engineers indicate some use of the area as early as the Middle Archaic Period (4,000 to 2,500 B.C.), only one county site, near Lewisville, has been deemed highly significant, and it is controversial. A Clovis point from the site was radiocarbon-dated at 37,000 B.C., but most other information contradicts the possibility that human beings inhabited the area that early. All other archeological work indicates nothing unique about prehistoric occupation of Denton County. There is no evidence that the county was the site of any large Indian villages in the Historic Period (1600–1800), although remains of many small transitory camps and small burial grounds have been found. Early Spanish and French explorers may also have trekked across the county, but documentation is lacking.
Anglo settlement began after William S. Peters, of Louisville, Kentucky, and several others, obtained a land grant from the Texas Congress in 1841. The land settled by their company, the Texian Land and Immigration Company, became known as the Peters colony. Their grant included all of the future Denton County, as well as parts or all of several other future counties. The earliest settlement in what became Denton County was in the southeastern section, near the site of present Hebron, and most of the early residents took up land in the Cross Timbers.
Although a few came from the lower South, most antebellum settlers in the area came from the upper South. In 1850, 40 percent gave Tennessee and Kentucky as their state of birth. Immigration from the upper South predominated because of the Kentucky-based Peters Company. The county was also limited to subsistence agriculture due to a lack of water transportation. Consequently, there were only 106 slaves in the county in 1850; in 1860, eighty-seven slaveholders owned 251 slaves.
In the 1840s Denton County was the site of the Icarian colony, a French utopian settlement north of the site of present Justin. The Icarians gave up and left after a few months of sickness and disappointment and made virtually no lasting mark on the county. The same cannot be said of the German community of Blue Mound, on the prairie a few miles northwest of Denton. Descendants of many of the German families that began settling there in the 1870s were still among the residents of the community a century later. Most were from Saxony, via Illinois or Missouri.
In 1846, the Texas legislature formed Denton County out of what had been a much larger Fannin County. It was named for John Bunyan Denton, an eastern Fannin County Methodist preacher and lawyer, who was killed in a raid against Indians in northern Tarrant County on May 22, 1841. A county seat, named Pinckneyville, was located near the center of the county, at a spot about a mile southeast of the present center of Denton. Although county officials were elected in 1846, no courthouse was built, and less than two years later a site named Alton, three or four miles to the southeast, was made county seat. Because water was not readily available, in 1850 the legislature allowed Alton to be moved about two miles south to Alexander Cannon's homestead near Hickory Creek. A log courthouse, the first in the county, was built there. Alton soon had stores, residences, and a hotel and was a regular stage stop. In the summer of 1856, however, county residents voted to establish a new county seat near the center of the county on a 100-acre tract donated by Hiram Cisco, William Loving, and William Woodruff. The new town, named Denton, was established the next year, but was not incorporated as a city until 1866.
Denton County grew slowly until after the Civil War. In 1860 it had 4,780 residents, slightly more than 10,000 acres of improved land, and a few more than 20,000 cattle, 6,000 of which belonged to John S. Chisum, who began ranching in the northwestern part of the county in 1854. Almost all residents were still engaged in subsistence agriculture. Cotton ginned that year totaled only two bales. Growth was rapid, however, in the decade of the 1870s, when the population grew from 7,251 to 18,143. Many new residents began farms, and in 1880 almost 50 percent of the county was in cultivation.
Railroads entered the county in the 1880s and had a great economic and demographic effect. Production of such subsistence crops as corn and vegetables declined, acreage in cotton and wheat increased rapidly, and the number of cattle grazing the prairies shrank substantially. Cotton acreage, 29,785 acres in 1880, peaked at 115,078 in 1920, but declined to insignificance in the 1980s. The Grand Prairie of Denton County was ideal for wheat culture, and between 1880 and 1900, wheat acreage increased by more than 80,000 acres. From 1890 to 1920 the county ranked either first or second in wheat production among the counties of the state, behind Collin County. Krum, a village near Denton, was reputed in 1900 to be the largest inland wheat market in the United States. Between 1880 and 1920 the number of beef cattle declined from 49,008 to 12,123, and 89 percent of county land was in cultivation at the latter date. Railroads also determined town location up to the 1970s, when only one town of any size was not on one of the railroad lines built in the 1880s.
Although Denton County's railroads made the county a significant agricultural producer, they did not make it an important commercial or manufacturing center. Consequently, population expansion in the twentieth century, slow in response to agriculture after 1900, depended to a great extent on other forms of transportation and on higher education. The county's population growth and its economic and cultural life were much influenced by the location in Denton of two large state-supported universities. The University of North Texas, established as Texas Normal College in 1890, had an enrollment of more than 20,000 in 1993. At the same time, Texas Woman's University, which originated in 1903 as Girls' Industrial College, had an enrollment of about 5,000 at the Denton campus.
Rubber-tired transportation and, perhaps to a lesser extent, the location of Dallas–Fort Worth International Airport, played a large part in the growth of Denton County after 1940. During World War II the county began to serve noticeably as a bedroom area for Dallas–Fort Worth. Completion of Interstate Highway 35 in the 1950s increased commuting, and in the 1980s Interstate highways 35E and 35W forked in Denton. All of the towns and cities of the county had a significant commuter element, but the southeastern portion, growing most rapidly, was virtually an extension of Dallas–Fort Worth. Lewisville, The Colony, and the part of Carrollton in Denton County were all population centers because they were suburbs of Dallas. The population of Denton had also grown because of the city's proximity to Dallas and because of the growth of the University of North Texas and Texas Woman's University.
The county population grew from 47,432 in 1960 to 143,126 in 1980. Many new rural residents owned small spreads, and mobile homes vied with expensive, sprawling ranchhouses for space. Large horse ranches were scattered through the county; in 1983 horses brought in $17,207,400, a significantly larger income than that from any other agricultural product (see HORSE AND MULE INDUSTRY). Newcomers and many older residents returned much of Denton County's rich cropland to pasture, and by the 1980s rural areas, almost depopulated by the rural-to-urban shift after World War II, had probably returned to their 1920s level in density of population.
Denton County voters supported the Democratic candidates in almost every presidential election from 1848 through 1948; the only exceptions occurred in 1860, when Constitutional Union candidate John Bell carried the county, and in 1928, when Republican Herbert Hoover did. Beginning in 1952, when Dwight D. Eisenhower won most of the area’s votes, the county’s voters shifted their allegiance to the Republican party, and thereafter supported the GOP’s presidential candidates in virtually every election from 1956 through 2004. The only exception occurred in 1964, when native-son Democrat Lyndon Baines Johnson carried the area.
The U.S. census counted 753,363 people living in Denton County in 2014. About 62.5 percent were Anglo, 18.9 percent were Hispanic, and 9.4 percent African American. Of residents age twenty-five and older, 89 percent had completed high school, and 37 percent had college degrees. In the early twenty-first century electronics and other light industries, horse-raising, and truck and missile manufactures were important elements of the local economy; many of the county’s residents commuted to Dallas to work. In 2002 the county had 2,358 farms and ranches covering 349,000 acres, 48 percent of which were devoted to pasture and 46 percent to crops. That year farmers and ranchers in the area earned $49,102,000; livestock sales accounted for $37,338,000 of the total. Horses, eggs, nursery plants, turf, and cattle were the chief agricultural products. The largest cities are Denton (population, 121,122) and Lewisville (100,237). Attractions include Lewisville and Grapevine lakes, the annual Denton Jazzfest in April, and the North Texas State Fair in August.