Dalhart, the county seat of Dallam County, straddles the border of Dallam and Hartley counties in the northwest corner of the Texas Panhandle.

The original settlement was platted early in 1901 by W. J. Blair and Charles W. Thornton when the Chicago, Rock Island and Pacific Railway built west from Liberal, Kansas, and crossed the Fort Worth and Denver City line. The site of the crossing was known for a time as Twist Junction. J. H. Conlen supervised the laying of the Rock Island tracks and made an old boxcar into a section house on the site.

Later the settlement was named Denrock, a combination of the names of the two railroads; in 1901 Robert B. Edgell named his new newspaper the Denrock Sun. But when postal authorities objected, the town adopted the name Dalhart, combining the first syllables of the names of the two counties in which it is located.

On June 11, 1901, Ora D. Atkinson and other promoters incorporated the Dalhart Town Company, and the first and only sale of lots was held on July 20. Dalhart was incorporated as a town on May 6, 1902, and as a city on April 6, 1904. It replaced Texline as Dallam county seat, as a result of an election on February 21, 1903. From that time on, Dalhart quickly grew as a shipping center for the XIT Ranch and other area ranches. The activities of the W. P. Soashqv Land Company also contributed significantly to Dalhart's progress. C. E. Williams, a noted well driller, built the town's first water tower in 1906. Previously, it had been necessary to buy water at twenty cents a barrel from barrels lining the railroad tracks.

By 1912 Dalhart had a population of 3,500. The two railroad lines, which erected machine shops, roundhouses, and a lever control tower, contributed to the town's prosperity, and Dalhart played a major role in establishing the Enid, Ochiltree and Western and other small railways. In addition, it had three banks, a flour mill, a large grain elevator, a planing mill, a modern utilities system, a hospital, an ice plant, several hotels and churches, and a high school athletic program serving an ever-expanding agricultural area. When oil companies began drilling in the Panhandle, Dalhart was among the first towns to sell oil leases.

The Dallam County Public Library, the first county library in Texas, opened for circulation in January 1921. Dalhart's population was further increased with the development of its East Heights addition in 1928. During the drought years of the 1930s Dalhart was notorious for its "black dusters". R. S. (Uncle Dick) Coon, a wealthy businessman who owned the DeSoto Hotel, became legendary for his generosity to depression-stricken farmers and cowboys. In August 1934 Dalhart became the site of one of the first three erosion-control demonstration projects in Texas, sponsored by the federal land bank, and the first to be devoted specifically to wind erosion. The Work Projects Administration and National Youth Administrationqqv also had chapters in Dalhart. Dalhart Army Air Field was established about two miles southwest of town.

In 1990 Dalhart remained an agribusiness center for a wide area of Texas, Oklahoma, and New Mexico. In addition to cattle feedlots, a bottling plant, and feed and meat processing plants, Dalhart is noted for its schools, hospital, and nursing home. The Dalhart Texan has served as the area newspaper since December 11, 1902. The Rock Island shops continue to help furnish the city's payrolls. Three U.S. highways, 87, 385, and 54, converge at Dalhart. Since 1936 Dalhart has been the home of the XIT Ranch Reunion and Rodeo, held in August. It was the XIT Reunion Association that built the landmark Empty Saddles monument and later established the XIT Museum. Another community event is the annual Railroad Week. Two miles south of Dalhart is Rita Blanca Canyon, site of Rita Blanca Lake. The city's population increased from 5,899 in the 1950s to 6,854 in the 1980s. In 1990 it was 6,246.