The Quarter Circle Heart Ranch was established when Lewis H. Carhart, the founder of the original Clarendon colony, invested part of his fortune in cattle. Since his colonization scheme occupied most of his time, Carhart initially ran only a few hundred head. The success of other large cattle companies, however, prompted him in 1883 to extend his own operations. His brother-in-law, Alfred P. Sully, of the New York investment firm of Austin and Corbett, visited Clarendon to arrange for a syndicate and then returned east to begin foreign negotiations, while Carhart worked to increase the herd and improve the ranch properties. The ranch had been under the temporary management of J. C. Murdock, but with its enlargement Carhart sought out an experienced cowman. He found him in Al S. McKinney, an Irishman who came highly recommended after having worked for the Spade Ranch. Early in 1884 a debenture company was founded in England, and Carhart sailed there to sell company stock to prospective buyers. Organization of the Clarendon Land Investment and Agency Company followed. After returning to assume the managerial responsibilities, Carhart registered his Quarter Circle Heart brand and added to his original holdings (343 sections) those of Frank Houston and S. V. Barton on McClellan Creek. Foreman Al McKinney took charge of the increased herds. Archie Williams, an elderly English veterinarian, was chosen to manage the new horse ranch that Carhart had established on the former Houston property. A dugout on Carroll Creek served as the first company headquarters; nearby was a two-room bunkhouse constructed of rock and sod. When McKinney was married, the ranch office was moved to the front room of his new house on an adjoining section. In addition, the ranch contained three division line camps. At its peak, the Quarter Circle Heart range covered 250,000 acres of land, in the center of which lay the town of Clarendon. Its longhorn cattle numbered from 15,000 to 35,000 head. Neighboring ranches included the JA, the RO, the Half Circle K, and the Diamond F. As the only settlement in their midst, Clarendon became the supply center and social hub. Noted cowboys who worked for the "Hearts" included Jesse S. Wynne, Frank Groves, Tom Martindale, Al Gentry, and Henry W. Taylor.
The prosperity of the Quarter Circle Heart was short-lived, especially after 1887, when Clarendon moved its townsite five miles south to the Fort Worth and Denver City Railway tracks. The drought and blizzard of 1886–87, the "Big Die-Up", had taken their toll. Increasing dissatisfaction among the company's British stockholders, many of whom had never received a dividend from their investments, prompted the executives to send the company secretary, Count Cecil Kearney, to the Panhandle for an on-the-spot investigation. Carhart and McKinney, upon learning that Kearney would arrive on a certain day, both resigned without notice and left Clarendon. Kearney's inspection tour revealed conditions worse than he had suspected. On the range where 35,000 head of cattle had grazed, he could find only a fraction of that number. Signs of gross mismanagement in all areas of the enterprise led to a complete reorganization, with Henry Taylor as range boss and Charles O'Donel, Kearney's nephew, as manager. Over the next few years, the Quarter Circle Heart range was divided into farms, school land, and settlements. By 1895 the brand had been discontinued.