The Handbook of Texas Online has an excellent biography:
Ben King (Doc) Green, writer, rancher, and veterinarian, son of David Hugh and Bird (King) Green, was born on March 5, 1912, in Cumby, Hopkins County, Texas. He moved with his family to Weatherford and attended high school there. He ran for a seat in the Texas legislature when he was about twenty-three years old, led the ticket in the primary, but lost in the runoff. As a boy Green fell in love with horses, and the love affair never ended. He bred horses and lived the life of a cowboy for most of his life, although he traveled widely outside Texas and the United States. At one time or another he both claimed and denied that he attended Texas A&M, Cornell University, and the Royal College of Veterinary Medicine in England, but most of his expert knowledge about animals came from experience. He began writing rather late in life, and it was a memorable moment when he met Alfred A. Knopf, the New York publisher, and told the international sophisticate more than he wanted to know about horses and cows and people. The result was that Knopf published Horse Tradin' (1967), Wild Cow Tales (1969), The Village Horse Doctor (1971), and Some More Horse Tradin' (1972), each a strong seller. The books were immediately hailed by critics, and Horse Tradin' has been cited as a classic of Western Americana. In 1973 Green received the Writers Award for contributions to Western literature from the Cowboy Hall of Fame in Oklahoma City. He also received a career award from the Texas Institute of Letters for his unique contribution to Texas literature.
Green wrote all of his books the way he operated best. He talked them, telling stories to a tape recorder and to his secretary. He wrote from his own experiences as a rancher, horse and steer trader, wild horse hunter, and horse doctor. He owned the only registered herd of Devon cattle in Texas and supported it on his farm in Cumby, where he also raised Percheron and quarter horses. He was in high demand on the lecture circuit.
He published eleven books between 1967 and 1974. His last, The Color of Horses (1974), was the product of his arduous research through the years on the hide and hair of horses to determine what made color. Although the book is controversial in content, Green considered it his most worthwhile contribution, and he saw it come off the presses shortly before he died of heart failure while sitting in his car on a roadside in northwest Kansas on October 5, 1974. Green was buried in a 100-square-foot knoll in the cemetery at Cumby. He thus made good his oft-repeated saying, "I never let myself be crowded in life, and by God, ain't nobody gonna close in on me when I'm dead!"
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Mr. Green was inducted into the Texas Trail of Fame in the Fort Worth Stockyards in 2014, and his star is on North Main Street. As mentioned in his biography, he has a section of Cumby Cemetery all to himself, and his headstone is of red granite, depicting a horse, with "Ben K. Green" above it. His dates of birth and death flank the horse. Complementing the headstone is a red granite footstone, with the same details. At each corner of the plot is Mr. Green's brand, a spur with the letter "G."