Abner (Ab) Pickens Blocker, trail driver, youngest of the three sons of Abner Pickens and Cornelia Randolph (Murphy) Blocker, was born on January 30, 1856, on the family ranch near Austin, Texas. He spent his youth in farm and ranch work and in 1876 joined his older brothers, William B. and John R. Blocker, on their range in Blanco County. In 1877 he helped deliver 3,000 steers to John Sparks in Wyoming. Over the next seventeen years he drove longhorn cattle up the trails from Texas to various buyers in Oklahoma, Kansas, Colorado, Wyoming, and Montana, and as far north as the Canadian border. In the summer of 1885 he delivered 2,500 head from Tom Green County to B. H. (Barbecue) Campbell, manager of the Capitol Syndicate's Buffalo Springs division in Dallam County. Campbell had contracted to buy cattle for the newly established XIT Ranch, and this was the first herd from South and West Texas to arrive. Blocker devised the XIT brand, for which the syndicate's ranch was named. Afterward he was involved in the dispute at Fort Supply, Oklahoma, resulting from the attempts of Kansas ranchers to quarantine the herds of his brother and other South Texas cattlemen and keep the Texans from crossing their land (see TEXAS FEVER).
Beginning in 1887 Blocker tried cotton farming for two years, but a period of drought soon put him back in the saddle. In 1890 he was made range boss of his brother's Chupadero Ranch, near Eagle Pass. His last overland trail drive was to Deadwood, South Dakota, with Harris Franklin's herd in 1893. In 1896 he married Florence Baldwin; they had a daughter. The family resided on a ranch in La Salle County, fifteen miles southeast of Cotulla, until a prolonged drought ruined them financially. In 1903, after living in Oklahoma for a year, the Blockers returned to Eagle Pass and subsequently took up residence again at the Chupadero Ranch. There they remained until 1912, when Blocker began working for the (later the Texas and Southwestern Cattle Raisers Association). He died in San Antonio on August 9, 1943, and was buried in Dignowity Cemetery.