With the loss of the war and continued Indian harassment, Slaughter and other ranchers started for Mexico in search of new ranch land. During the expedition Slaughter suffered an accidental gunshot wound that incapacitated him for a year, causing a nearly ruinous decline in his cattle business. After his recovery he started a cattle drive to New Orleans in late 1867, but en route contracted with a buyer for a Jefferson packery to sell his 300 steers there for thirty-five dollars a head in gold, a large sum. With his new stake he began regular drives to Kansas City in 1868, selling his herds for as much as forty-two dollars a head. He sold his Texas ranching interests in 1871 and in 1873 organized C. C. Slaughter and Company, a cattle-breeding venture, which later pioneered the replacement of the poor-bred longhorn with Kentucky-bred blooded shorthorn stock. By 1882 a herd shipped to St. Louis received seven dollars per hundred pounds.
In 1873 Slaughter moved his family to Dallas and a few years later dissolved his partnership with his father. About 1877 he established one of the largest ranches in West Texas, the Long S, on the headwaters of the Colorado River and there grazed his cattle on the public domain. Desirous of becoming a "gentleman breeder," he purchased in 1897 the Goodnight Hereford herd and the 1893 Chicago World's Fair grand champion bull, Ancient Briton. In 1899 he acquired the famous Hereford bull Sir Bredwell for a record $5,000. Through these purchases Slaughter's purebred Hereford herd became one of the finest in the business. Around 1898 Slaughter undertook a major land purchase in Cochran and Hockley counties. He bought 246,699 acres, leased more, and established the Lazy S Ranch, which he stocked with his Hereford herd and mixed breed cattle from the Long S and consigned to the management of his eldest son.
In 1877 Slaughter helped organize the Northwest Texas Cattle Raisers' Association (later the Texas and Southwestern Cattle Raisers Association), for which he also served a term as president (1885). He was the first president of the National Beef Producers and Butchers Association (1888), an organization formed to combat market domination by the meat-packing industry. Frequently titled the "Cattle King of Texas," Slaughter became one of the country's largest individual owners of cattle and land (over a million acres and 40,000 cattle by 1906) and was the largest individual taxpayer in Texas for years. For a time "Slaughter Country" extended from a few miles north of Big Spring 200 miles to the New Mexico border west of Lubbock. By 1908-09, however, he opened his Running Water and Long S Ranches to colonization and sale. Yet by 1911, much of the land reverted to his ownership upon the failure of the land company promoting colonization there, and under the management of Jack Alley, it was restored to profitability by 1915. Slaughter maintained strict control over his operations until 1910, when he suffered a broken hip that crippled him for the remainder of his life, compounding problems caused by his failing eyesight. He consequently turned the business over to his eldest son, George.
In addition to ranching, Slaughter participated in banking in Dallas where he helped organize City Bank in 1873 and invested in the bank's reorganization as City National Bank in 1881; at that time he became its vice president. In 1884 he helped establish the American National Bank, which evolved by 1905 into the American Exchange National Bank (later First National Bank). He was vice president from its organization until his death. On December 5, 1861 (possibly 1860), Slaughter married Cynthia Jowell of Palo Pinto, Texas; they had five children. After being widowed in 1876, he married Carrie A. Averill (Aberill) in Emporia, Kansas, on January 17, 1877; they had four children. Slaughter was a Democrat and Baptist; he contributed two-thirds of the cost for the construction of the First Baptist Church in Dallas and served as vice president of the Southern Baptist Convention, as president of the state Mission Board (1897-1903), and as an executive board member of the Baptist General Convention of Texas (1898-1911). His support of a plan to retire the consolidated debt of seven Texas Baptist schools and coordinate their activities into a system capped by Baylor University assured its acceptance by the general convention in 1897. Slaughter also contributed generously to the establishment of the Texas Baptist Memorial Sanitarium (later Baylor Hospital) in Dallas. He died at his home in Dallas on January 25, 1919.
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