Dalhart is a city in Dallam and Hartley Counties in the U.S. state of Texas, and the county seat of Dallam County. Dalhart city was founded in the year 1901. Dalhart is named for its location on the border of Dallam and Hartley Counties; its name is a portmanteau of the names of the two counties. The city was founded at the site of a railroad junction, which heavily contributed to its early growth. Dalhart is known as the “XIT City” because of its relationship with the historic XIT Ranch.