Rockwall County is on the Blackland Prairies of north central Texas at 32°55' north latitude and 96°25' west longitude, twenty-five miles northeast of Dallas. Rockwall County is the smallest county in Texas. Its 147 square miles of flat, undulating, and gently rolling prairie ranges in elevation from 390 to 620 feet above sea level. The almost square county has three distinct topographic divisions: the valley of the East Fork of the Trinity River; a small area of gently undulating to steeply sloping terraces west of the valley; and rolling uplands east of the valley, which cover 80 percent of the county. The light to dark soils are slightly acidic and have loamy to clayey surfaces and cracking, clayey subsoils. Ninety-three percent of the county is arable and extremely fertile. The greater part of Rockwall County is a treeless prairie, although there was once heavy timber along the East Fork of the Trinity River. Along the creeks and in the bottoms there are a variety of hard and softwood trees, including bois d'arc, elm, oak, mesquite, and pecan. In the eastern part of the county grow tall bunch grasses, while shorter grasses are found to the west. There are a few native grass hay meadows, but most of the pasture land is in bermuda, clover, or Johnsongrass. All parts of the county are well watered by springs and small lakes. The area did not have a large, navigable body of water until the East Fork of the Trinity River, which runs north to south along the western border the county, was dammed to form Lake Ray Hubbard. The lake, built to supply water for Dallas, now covers 13.55 percent of Rockwall County. Except for a small section of the northeastern part of the county, which drains into the Sabine Creek, all streams empty into the East Fork. The growing season is 236 days, with an average annual precipitation of 38.68 inches. The temperature ranges from an average high of 96° F in July to an average low of 34° in January. There are no mineral resources, except for a small amount of native stone.
The region around Rockwall County was the home of several tribes of Caddo Indians. Cherokees from east of the Mississippi began to arrive in the area early in the nineteenth century, and as they spread, they almost annihilated the peaceful, agricultural Caddoes. When the first Anglo-Americans arrived in the valley of the East Fork of the Trinity sometime in the 1840s, they found these various Indian groups at war among themselves. The White settlers in the area seem to have had little problem with them, however. The National Road of the Republic of Texas was surveyed and constructed in the mid-1840s through the area that would become Rockwall County. Running northeast from the Dallas area to the Red River, the road was a major route for settlers traveling to Peters colony near the site of present-day Dallas. In 1846 the first settler, John O. Heath, received a grant from the Mercer colony and established his home on the East Fork of the Trinity River near the crossing of the Central National Road. Occasionally when the swollen waters of the Trinity River prevented crossing, some families simply settled along the east bank of the river. The towns of Heath and Rockwall were thus founded along the highway. The first post office in the area was established in the Heath cabin in 1849 and named Black Hill. It operated there until 1855, when it was transferred to the new village of Rockwall. During the 1850s other families continued to settle along the river, while some moved eastward to the prairies to establish cattle ranches. Cattle raising was the principal industry in the first years of settlement, although small lots were fenced for cultivation, and razorback hogs were raised. A total of 240 pioneers came to hold original titles from the state. Several farmers were digging a well in 1851 when they discovered a subterranean rock wall or diker that crossed the county and occasionally appeared at ground level. Although scientific analysis indicated that the wall is a natural geological formation, folk tales persist that it was built by prehistoric natives. When it was surveyed and laid out in 1854 the town of Rockwall was named for the curious rock formation. In 1836 the area was established as part of Nacogdoches County, and when Texas joined the Union in 1845, it was included in Henderson County. Kaufman County was formed in 1847, and the region now known as Rockwall County was placed in the jurisdiction of the new county. In 1873, because the county seat, Kaufman, was inconvenient for the residents of the northern panhandle, Rockwall County was formed, taking its name from the town and geological formation. Rockwall was the first county seat and continues to hold that position, although in 1892 there was an unsuccessful attempt to make Fate the county seat. In 1873 Rockwall was incorporated.
Coincidentally, about the same time that Rockwall County was being established, there was a significant change in the economy of the area. Although a little cotton and considerable amounts of wheat and corn were grown before the Civil War, difficulty in transporting the products across the river and over rough wagon roads to the market in Dallas discouraged extensive commercial agriculture. When the Texas and Pacific Railway was built through Kaufman County in 1873, much of the agricultural produce of Rockwall County was taken there for shipment. The combination of better transportation, a cotton gin built in 1866, and fertile land encouraged farmers to produce cotton on a large scale. The Missouri, Kansas and Texas Railroad built through the county in 1886 and gave impetus to settlement. By 1890 there were 5,972 residents in the county. The 50 percent increase in population from 1880 was composed almost entirely of White Americans. African Americans, the only other significant racial group, comprised only 3 to 5 percent of the total. The number of farms increased from 526 in 1880 to a county record of 1,090 in 1900. The same years saw a steady rise in the production of cotton, the principal cash crop of the area. Manufacturing and nonagricultural business remained small in the last decades of the nineteenth century. In 1900 only fifty people were employed in manufacturing establishments in the county. From 1900 until 1930 cotton production increased, reaching a high in 1930 of 18,987 bales. Cattle raising continued to decline in importance; in 1930 only 752 non-milk cows were reported in the whole county. The number of farms remained fairly stable, although farm values dropped 60 percent in the years from 1920 to 1930. The Great Depression left 15 percent of the available workers with relief jobs or in search of work in 1940. Through the agency of the Work Projects Administration, a new courthouse was constructed to replace the old one built in 1893. The population in the county fluctuated between 8,000 and 8,500 during the first decades of the new century. Throughout this time, though, there was a steady decrease in the number of White citizens. The Black population, largely rural, steadily increased in actual numbers and in the percentage of the total population. In 1930 1,955 residents (25 percent of the population) were Black.
The economic structure of the area was altered in 1940 because of the great number of workers commuting to industrial jobs in Dallas. It was estimated that in 1948 one-third of the labor force living in Rockwall County was employed in Dallas. The county continued to show a decline in population, with a total of 7,071 residents reported in the 1940 census. Further decline occurred during World War II, when 1,233 persons left to serve in the armed forces or obtain work in industry. By 1948 some of the war losses had been regained, but the county continued to lose people until in 1960 only 5,872 residents remained. During these same years the Black population began to drop slowly. However, it still remained 25 percent of the total population.
In 1955 52 percent of the residents were considered non-farm rural. A few manufacturing plants were established, including garment, leather goods, and aluminum processing factories. Other nonagricultural income came from rail and highway commerce. The city of Rockwall, with 2,166 residents in 1960, had a seed-cleaning plant and feed mill and was a commercial center for the thickly settled farming region. Royse City, in the northeastern part of the county, was a shipping point for cotton and other agricultural products. Some gradual shifts had occurred in agriculture. During the 1930s cotton production was reduced, and diversified farming practices were introduced. Cotton farming continued to be the major industry in the county, but production began slipping. By 1959 the crop was down to 7,466 bales a year, half of the 1940 crop. Meanwhile, the 1940s and 1950s showed a renewed interest in livestock production because the proximity of a growing population in Dallas gave the farmers a ready market for their meat. This trend toward livestock raising resulted in 5½ times as much land being used as pasture in 1948 as had been used in 1925. As agriculture began to lose its dominance in the county, the number of farms dropped from 1,031 in 1930 to only 320 in 1959. However, the same period showed an increase in farm values, from a low in 1940 of $4.7 million to $18.9 million in 1959. The use of mechanical devices increased on the farms, and most rural residents had electricity available by 1948.
The years between 1960 and the late 1980s saw impressive changes in Rockwall County, as it became more a part of the greater Dallas metropolitan area and less a small rural county. This trend had begun years earlier, during the depression and World War II, but was greatly influenced by several major developments. The first of these was the completion of Interstate Highway 30 in the late 1950s. This highway, which enters the county midway on its western border with Dallas County and passes by Rockwall and Royse City to exit in the northeastern corner, provides easy access to Dallas and facilitates shipping into and out of the county. In the mid-1950s Lake Lavon, on the East Fork of the Trinity River just to the north in Collin County, was constructed. It protected the river valley from flooding, increased the available water supply for the area, and provided Rockwall County with income from the recreation and tourist industry. Probably the most dramatic change was brought about with the construction of Lake Ray B. Hubbard in 1969 and 1970. Although a significant portion of the land in Rockwall County was flooded, and the county lost some tax revenue from that, new housing developments around the lake and other recreation added more income than was lost. The trend away from agriculture continued; only 191 farms were reported in 1982. Crop production was low, and wheat, hay, sorghum, and oats had replaced cotton. Stock raising however, remained high; 16,000 cattle were reported in 1982. In spite of the loss of acreage, total farm values increased threefold from the 1969 value of $29.5 million, an indication of higher land prices due to the increased demand as more people moved in. Manufacturing increased. In 1967 only five establishments were in operation, and in 1982 twenty-six firms had a total of 700 employees. The industries with the most employment were agribusiness and manufacturing of women's clothing and aluminum products. In 1982 the county had 17,066 registered vehicles, 307 miles of paved roads, intercity bus service, motor freight, rail, and the Rockwall Municipal Airport. Total employment tripled from 1970 to 1984, when 3,554 people worked in various jobs throughout the county. Almost two-thirds were employed in construction, service, retail trade, finance, insurance, and real estate, services that are in high demand by the affluent residents of the metropolitan suburb. In 1967 Rockwall County's closer ties with Dallas were acknowledged when the county was added to the Dallas Standard Metropolitan Statistical Area.
The population grew accordingly. In 1970 7,046 people lived in the county. Rockwall County ranked thirty-third among all United States counties in growth rate for the years between 1970 and 1980. In 1990 the population reached 25,604. Many of the new residents commuted to Dallas, and many were financially well off. In 1999 Rockwall County's median household income was $65,164, ranking it second among Texas counties. The influx of white-collar workers has also helped to improve the area's education level. Of the residents over age twenty-five in 1950 only 21.5 percent had a high school education, but of the same group in 1980 70.3 percent had completed high school, and 20.3 percent were college graduates. By 2000 almost 87 percent had high school diplomas, and almost 33 percent had college degrees.
The same period also saw a shift in political affiliation. For most of its history the county had always had strong Democratic leanings. Even in 1952 and 1956, when 53 and 55 percent of the rest of Texas voted for Dwight D. Eisenhower, the Republican candidate, 66 and 58 percent of Rockwall County voted for the Democratic candidate, Adlai Stevenson. From 1972, when Republican Richard Nixon carried the county, through 2004, however, the county consistently voted Republican in presidential elections. Other changes occurred in the characteristics of the population. By 1980 there were only 731 Blacks living in the county, about 5 percent of the total population.
In 2014 the census counted 87,809 people living in Rockwall County. About 72.8 percent were Anglo, about 6.1 percent were African American, and 16.7 percent were Hispanic. In the early twenty-first century local industries and employment with Dallas companies were the mainsprings of the county's economy. In 2002 the county had 385 farms and ranches covering 46,419 acres, 54 percent of which were devoted to crops and 42 percent to pasture. In that year local farmers and ranchers earned $2,999,000, with livestock sales accounting for $1,945,000 of that total. Small grains, cattle, horticulture, and horses were the chief agricultural products. Most of the people in the county lived in either Rockwall (population, 41,147), the county's seat of government; Royse City (10,338); Heath (7,704); or McLendon Chisholm (1,672). Rockwall County's proximity to Dallas and the lure of its large, peaceful homes near the lake have made it a growing suburban county. Royse City hosts a Funfest in April and is home to the North Texas Speedway.