Andrew Briggs (Sug) Robertson, rancher and banker, the sixth of eight children of Dr. A. B. and Rachel Jewell Robertson, was born January 14, 1855, on a farm in Indiana. His famous nickname was allegedly derived from an elderly country physician, Dr. Sug, whose toothless countenance the child resembled before his teeth developed. In 1861, before the Civil War, his father, a renowned scientist and physician originally from Virginia, moved the family to Arkansas; the family moved in 1863 to Hood County, Texas, where they located on the Brazos River. Dr. Robertson rejoined his family there in 1865 after serving as a surgeon in the Confederate Army. In later years he moved to Louisiana and became noted for his lectures in astronomy. With their parents' consent, ten-year-old Sug and his older brothers were hired out at $7.50 a month to do ranch work for R. K. Wylie's open-range outfit. Sug proved himself an adept cowhand and accompanied the Wylie cattle on drives to Coleman and Runnels counties. He endured the hazards of the trail, including brushes with Comanches, and stayed with Wylie for ten years, much of which he spent on Wylie's Flat Top Ranch in Coleman County. Having had only six months of formal schooling, Sug learned to read and write by studying newspapers by the light of the campfire at night and by practicing penmanship on his boots, using bills of sale for camp supplies as models. In 1871 he met John Simpson Chisum, who was trailing his herds through Coleman County to New Mexico; he once helped Chisum prevent a disastrous stampede. Chisum became the teenage cowboy's hero. All five Robertson brothers became successful cattlemen.
In 1873, at the age of eighteen, Sug Robertson was made range manager of all the Wylie cattle. In that position he drove a herd of 1,500 head from Coleman County to Coffeyville, Kansas, then a leading railroad shipping point. The following year Robertson went into partnership with Wylie and purchased 5,000 head, roughly a half interest in the Runnels County herd. After the Indian menace subsided in 1879, Robertson sold this interest back to Wylie and bought the latter's herd of 3,000 on the Pecos River near Horsehead Crossing. His legendary diplomatic agreement with local rustlers kept this herd, which carried the TX brand, intact with no thefts. The basis for Robertson's fortune came in 1882, when he sold the TX herd to John Dawson and netted $50,000. With his new earnings he moved to the booming rail town of Colorado City. There in 1883 he helped organize the First National Bank and was elected its vice president. At the same time, he and his brother W. C. bought a 19,000-acre ranch on Silver Creek in Nolan County. Although the 1880s was a time of financial disaster for cattlemen due to reckless management and inflated prices, Robertson weathered the crisis and recovered his losses by purchasing and delivering range cattle on a large scale. On May 30, 1887, he married Emma Lenora Smith, daughter of a Runnels County stock farmer, in Coleman. They became the parents of five children, four of whom eventually followed their father's footsteps in the cattle business. One daughter died in infancy. Robertson was elevated to the presidency of his Colorado City bank in 1889.
In 1890, after turning the Silver Creek ranch over to his brother, he formed a partnership with Winfield Scott of Fort Worth. They purchased 50,000 cattle and placed them on choice rangeland in Gaines County, Texas, and Eddy County, New Mexico. R. P. (Dick) Robertson, Sug's brother, was made manager of this million-acre spread, on which the Hat brand was used. Another significant gain for Robertson and Scott occurred in 1900, when they purchased 125,000 acres in Lubbock, Lynn, Garza, and Crosby counties after the failure of the St. Louis Cattle Company's trust scheme. This ranch, with headquarters established near Slaton, supplied range for 10,000 cattle. For a brief time Robertson also owned 25,000 acres in Borden County. This made him the largest individual landowner on the South Plains of Texas, although by 1906 most of the Hat range had been parceled out to settlers and the cattle shipped north to ranges in Montana. Between 1902 and 1905 Robertson became sole possessor of 35,000 acres of the former St. Louis Company ranch and began using a V brand, which he had registered in Nolan County in 1890. In 1908 he moved his family to Fort Worth, but three years later they returned to live at his commodious ranchhouse near Slaton. That town's South Park addition grew from land Robertson deeded to developers in 1910.
During his later years Robertson served on the board of directors of the Cattle Raisers Association of Texas and was a member of the National Livestock Association's Executive Committee. He advertised his cattle-raising methods in agricultural journals and owned two, the West Texas Stockman and the Weekly Clipper. Robertson's reputation as a storyteller always won him an audience at various cattlemen's conventions nationwide. He accurately predicted the future of West Texas as a leading agricultural region and continually preached that "the world can't hold down the man who is determined to succeed and who proceeds fearlessly at his task." Robertson died in Abilene supposedly of acute indigestion on February 12, 1921, while he and his wife were visiting their son. He was buried in the Odd Fellows cemetery in Colorado City. His widow continued to manage the family's ranching interests until her death following a stroke at Slaton on April 25, 1944. She was buried at Colorado City.