San Patricio County is on the lower Gulf Coast in the Coastal Prairies region, bordered on the north by Bee County, on the northeast by Refugio County, on the east by Aransas County, on the southeast by Nueces County and Corpus Christi Bay, and on the west by Jim Wells and Live Oak counties. The county's center lies at 29°03' north latitude and 97°33' west longitude. Sinton, the county seat, is just northeast of the center of the county sixteen miles north of Corpus Christi. San Patricio County covers 693 square miles of generally flat land with tall prairie grasses spotted by mesquite and live oak trees. Most of the county lies in the coastal plain, but in the far western area the surface is rolling with some caliche hills; elevations range from sea level to 200 feet. Soils consist of light to dark loam on the surface, with clayey subsoils. The area is drained by the Nueces River on the south and the Aransas River on the north, with Chiltipin Creek draining the north central portions. San Patricio County has a mild, moist climate, with an average annual rainfall of thirty-one inches. Temperatures range from an average low of 46° F in January to an average high of 93° in July. The average growing season lasts 303 days. The area supports a wide variety of wildlife species, including deer, javelina, rabbit, raccoon, and coyote, as well as wild fowl such as duck, geese, crane, and turkey. The Rob and Bessie Welder Wildlife Foundation and Refuge supports research of native fauna. In 1982, 93 percent of the county's land was in farms and ranches. About 68 percent of agricultural income derived from crops, particularly sorghum grain, cotton, and corn, and lesser acreages of vegetables and feed crops. Livestock, especially cattle and hogs, also contributed to the local economy. Natural resources include industrial sand, caliche, natural gas, and petroleum. In 1982, 37,904,000,000 cubic feet of gas-well gas, 3,648,000 barrels of petroleum, and 4,800,000 cubic feet of casinghead gas were produced in San Patricio; caliche was mined in the western part of the county.
Artifacts such as projectile points associated with the late Paleo-Indian and Early Archaic cultures have been found in the county, suggesting that the area has been inhabited by humans for at least 6,000 years, and perhaps much longer. The Karankawa Indians, linked by anthropologists to an archeological complex called the Rockport Focus, probably moved into the area about A.D. 1400. Hundreds of Indian campsites have been identified in San Patricio County. A number of Spanish and French explorers, including Alonso Álvarez de Pineda, Alonso De León, Jean Béranger, Diego Ortiz Parrilla, and José de Evia traveled through what is now San Patricio County. An expedition led by Pineda explored the bays behind Aransas Pass in 1519, while De León's expeditions of 1689 and 1691 sailed up and down the coast investigating the bays and probably entered Aransas Pass. Béranger's trips into the bays are well chronicled in his own journal. In 1712 and 1718 a party of French came ashore on St. Joseph Island, and later Ortiz Parrilla was instrumental in advancing the knowledge of the area with his explorations in the Nueces River valley. José de Evia made the field notes that turned into the Langara map, which features this area. Mexican sheepherders also camped in what is now San Patricio County before the era of colonization.
In 1828 empresarios John McMullen and James McGloin contracted with the government of Mexico to settle 200 Irish Catholic families on eighty leagues of land in the area. The first groups of families, recruited from the Irish population of New York, landed at El Cópano and Matagorda in late 1829; two other groups soon followed. After a brief stopover at the old Refugio mission, the colonists proceeded to the north side of the Nueces River and established the town of San Patricio de Hibernia, named after the patron saint of Ireland. In 1834 the colony was legally established as the Municipality of San Patricio in the Mexican state of Coahuila and Texas. By 1836 eighty-four land grants had been made in the colony, and about 500 people were living there. The area was engulfed in fighting during the early stages of the Texas Revolution. Fort Lipantitlán, built in 1833 across the Nueces near the colony, surrendered to a company of the colony's settlers in 1835. In February 1836 a detachment of Texans commanded by Francis W. Johnson encountered a Mexican force in the town of San Patricio. All but four of the Texans were killed or captured. Most of the colonists subsequently moved to Victoria and other havens. San Patricio County was established in 1836 by the Congress of the new Republic of Texas. Far larger than the current county, the original San Patricio County included territory later incorporated into other counties. Its original residents were slow to move back into the area, however, for fear of the periodic Mexican incursions; a Mexican force under Gen. Ráfael Vásquez raided the San Patricio area as late as 1842. The county was officially designated a "depopulated area" by the government during most of this time, though traders, soldiers, and various adventurers traveled through. By 1841 San Patricio County once again had a small number of more or less permanent residents. The area was not really stabilized, however, until Gen. Zachary Taylor moved his army into the region after Texas was annexed by the United States in 1845. Taylor's army briefly camped near the site of present Rockport, and after the Mexican War began, reinforcements and supplies for the American army flowed through the county. In 1845 Corpus Christi was designated the county's seat of government and remained so until 1846, when San Patricio County lost all of its territory south of the Nueces River to the newly established Nueces County. That year the town of San Patricio became San Patricio County's seat. In 1848 more new counties were formed, and the county was further reduced in size.
In 1850 the county was only beginning to recover from the turmoil and dislocations occasioned by the Texas Revolution. The United States census counted only 200 people, including three slaves, living in the area. According to the agricultural census for that year, farms in the county encompassed 40,465 acres. Cattle raising remained the focus of the local economy. About 500 milk cows, 1,200 cattle, and 150 sheep were reported. Crop cultivation had not yet become established. Only 4,400 bushels of corn, the county's most important crop at that time, were produced that year. With the threat of raids by the Mexican army removed and the Indians pushed out of the area, more people began to move into the county. John G. Hatch settled in the southeastern part of the county area in 1854, and the Engleside post office was soon established on the Cross S Ranch. Youngs Coleman established a ranch on Chiltipin Creek about the same time. The White brothers, Eddie and Frank, settled in the White Point area in 1856, and William Marshall Means established Meansville in the southern part of the county before 1860. Cattle drives moved out from the area in the late 1850s, providing the area's main source of income; meanwhile, crop cultivation was slowly spreading in the southeastern section of the county. In 1858 the county was reduced in size one last time, and its present boundaries were established. By 1860 the population had increased to 620, including ninety-five slaves. That year there were fifty-one farms and ranches (three acres or larger) in the area. Cattle continued to dominate the local economy. More than 48,000 cattle were reported in San Patricio County in 1860; almost 4,000 sheep, producing 6,440 pounds of wool, were also reported. Meanwhile only 1,700 acres were described as "improved," and only 475 bushels of corn, along with small amounts of sweet potatoes, potatoes, beans, and peas, were produced that year. The Civil War brought further changes. While the area was far removed from the main battle lines, it was on the "Cotton Road" to Matamoros, Mexico, which became a major center of cotton smuggling after the Union government imposed a blockade on the South. A Confederate fort was built at Aransas Pass, federal ships appeared in 1862 to harass smugglers, and federal raiding parties periodically came ashore near Ingleside, burning houses and confiscating livestock. During the war the county was also plagued by bands of rustlers who preyed on local herds. To avoid various threats to their well-being, many people living in the Ingleside area felt compelled to move to Goliad during the war. Meanwhile, the hanging of Josefa (Chipita) Rodríguez in 1863 demonstrated the prejudice many Whites in the area harbored against Mexicans and Mexican Americans.
Towards the end of the Civil War and in the years immediately following, settlers from other parts of the south in search of cheap land moved into San Patricio County. The new immigrants were especially concentrated in the southern parts of the county. Around 1870 Sidney G. Borden started Sharpsburg, which soon outstripped San Patricio in population and was the county's only port. By 1870 there were 602 people, including sixty-four Blacks, living in San Patricio County. The agricultural census reported fifty-one farms and ranches, encompassing 52,000 acres, in the area; about 2,400 acres were described as "improved." While ranching continued to dominate the local economy, crop cultivation was beginning to take hold, and 21,325 bushels of corn were produced that year. In 1871 Thomas M. Coleman and George W. Fulton joined with J. M. and Thomas H. Mathis in a partnership that formed the largest cattle firm in Texas. The Coleman, Mathis, and Fulton partnership, which held acreage in San Patricio, Goliad, and Aransas counties, flourished until an eighteen-month drought in 1878–79 wiped out much of its stock. When the partnership was dissolved in 1879 T. H. Mathis, who was awarded 64,000 acres of the firm's land, began plans to develop a townsite on his property. The remaining partners formed the Coleman-Fulton Pasture Company in 1880. The ranch headquarters was established at Rincon, seven miles north of the site of present Gregory; the headquarters soon became a community with its own school. The United States census counted 1,010 people living in the county in 1880, but the area's ranching economy had been ravaged by the drought. There were only thirty-six farms and ranches in 1880, and fewer than 7,000 cattle were reported that year. About 1,200 acres were planted in corn, the county's most important crop at that time; six acres were planted in cotton. The economy began to develop more rapidly after 1885, when the San Antonio and Aransas Pass Railway was built to the newly laid-out Aransas Harbor. By the 1890s towns such as Mathis, Sinton, and Gregory had been established along the railroad. Development of the area was significantly encouraged by out-of-state investors, especially David B. Sinton, a wealthy Ohio banker who was an old friend of Fulton's. Sinton and his son-in-law, Charles P. Taft, became major partners in the Coleman-Fulton Pasture Company. The ranch soon became known as the Taft Ranch. In 1893, after the Coleman-Fulton company donated 640 acres for a townsite near the center of the county, the Sinton Town Company was formed to develop the site. The new town, called Sinton, became the county seat later that year. In 1896 the St. Louis, Brownsville and Mexico Railway began to build into the county. Rockport, established in neighboring Aransas County in 1898, was envisioned by ambitious developers as a deep-water port that would serve as the hub of an extensive transportation network. Land values in the area began to rise significantly, though the population was still growing very slowly; as new towns appeared in the county, old settlements like San Patricio and Round Lake began to fade away. By 1900 there were 1,312 people living in the county. The agricultural economy recovered and grew during this period. By 1900 there were 190 farms and ranches, encompassing over 102,000 acres, in San Patricio County, and 34,000 cattle were reported in the area. About 2,000 acres were planted in corn that year, and 2,100 acres were devoted to cotton.
The development of the county intensified during the first years of the twentieth century, and particularly after 1909, when land agents began to widely advertise San Patricio County property to prospective farmers. New towns such as Odem (1904), St. Paul (1909), Edroy (1910), Taft, and Sodville sprang up along the railroads, as hundreds of new farmers moved into the area from northern Texas and other states. Meanwhile, trainloads of laborers were brought in from Mexico to clear the land of mesquite and prepare it for farming; large numbers remained to work in the fields, shaping the cultural and social development of the area. There were 470 farms in the county by 1910 and 757 farms by 1920. Meanwhile, the population grew to 7,307 by 1910 and to 11,386 by 1920. Though ranching remained important, crop farming emerged during this period as the most important element of the agricultural economy. Many farmers produced vegetables for urban markets, but cotton became the area's most important crop. About 15,000 acres were planted in cotton in 1910, and more than 60,000 acres in 1920; by 1930, 155,000 acres in the county were devoted to growing the fiber. As ranchland was converted to cropland the number of cattle dropped from 41,145 in 1910 to 17,006 by 1930. There were 1,626 farms in the county by 1930, but many of the new farmers did not own the lands they worked. Farm tenancy rates increased along with the expansion of cotton cultivation. By 1930 more than two-thirds (1,128) of the county's farmers were tenants; only 342 fully owned their lands.
Oil and gas discoveries in the region during the 1910s and 1920s helped to diversify the local economy, and in 1926 a gas pipeline was laid from neighboring Refugio County gasfields to Aransas. San Patricio County's population more than doubled during the 1920s, and by 1930 there were 23,836 people living there. Many farmers suffered during the Great Depression of the 1930s. Low prices, federal crop restrictions, and other factors combined to drive tens of thousands of acres out of production. Cropland declined from 179,279 acres in 1930 to 149,462 acres in 1940; cotton acreage fell by more than a third during this period. Hundreds of farmers were forced off the land, and by 1940 only 1,089 farms (and only 557 tenants) remained in the county. These setbacks were offset to some extent, however, when the county's oil and gas industry grew significantly during the mid-1930s. In 1938, 6,087,000 barrels of oil were produced in the county.
The area's population grew to 28,871 by 1940, and agriculture revived during the 1940s, but farm mechanization and consolidation led to a continuing decrease in the number of farms. By 1959 there were only 816 farms (393 operated by tenants) in the county. Though cotton production remained relatively high, sorghum became an increasingly important crop. The area's petroleum industry continued to flourish until the 1970s, when production began to decline significantly. Almost 10,870,000 barrels of oil were produced in the county in 1944, 16,166,000 barrels in 1956, over 11,764,000 barrels in 1960, and 10,254,000 barrels in 1965. Production dropped to 5,780,000 barrels by 1974, however, and to 3,648,000 barrels by 1982. Just under 2,078,000 barrels of crude were produced in 1990; by January 1, 1991, 468,841,000 barrels of oil had been taken from Patricio County lands since 1930. Meanwhile, the county's population increased to 28,871 by 1950, to 35,842 by 1960, to 47,288 by 1970, and to 58,013 by 1980. In the 1980s Reynolds Metals operated a plant on Corpus Christi Bay to extract alumina from bauxite, which was shipped in from Africa, Australia, and Brazil. Dow and Occidental chemical companies also had large plants on the ship channel in the 1980s. Two of the world's largest marine rig builders operated on the bay, and Ingleside was designated the homeport for the United States Navy's Battleship Wisconsin battle group. Aransas Pass was home to about 300 shrimp boats (see SHRIMPING INDUSTRY), and seafood landed in Aransas Pass and Ingleside earned more than $60 million annually. In 2014 there were 66,915 people living in the county. About 40.8 percent were Anglo, 2.1 percent African American, and 55.4 percent Hispanic.
The voters of San Patricio County supported Democratic candidates in virtually every presidential election between 1848 and 1988. The only exceptions occurred in 1928, when a majority voted for Republican Herbert Hoover; in 1972, when they backed Republican Richard Nixon; and in 1982, when Republican Ronald Reagan took the county. In the 1992 presidential election, a plurality of voters supported Democrat Bill Clinton over Republican George Bush and Ross Perot, the independent candidate. There are eight incorporated cities in the county, including Sinton (population, 5,712), the seat of government; Mathis (4,973); Odem (2,415); Taft (3,056); Gregory (1,926); Portland, (15,553, partly in Nueces County); Ingleside (9,605); Aransas Pass (8,305, partly in Nueces and Aransas counties); and San Patricio (387, partly in Nueces County). Edroy and St. Paul are not incorporated. Special events include the World Champion Rattlesnake Races held at San Patricio in March, the Fish-A-Rama held in Mathis each May, and the Shrimporee held in Aransas Pass each May. Taft hosts a Boll Weevil Festival in September, and an Old Fiddler's Festival is held in Sinton in October.