From the Annals of the County Seat – In 1902, Dalhart was recognized as the county seat of Dallam County. The name Dalhart is a portmanteau combining the name of the Dallam and Hartley counties as the town straddles the county line.  The town origins go back to the crossing of the Chicago, Rock Island and Pacific Railroad  and the Fort Worth and Denver line.  The settlement was first known as Twist Junction and later as Denrock derived from the names of the railroad lines.  However, when the postal service objected to the name, it was changed to Dalhart.

Photo from braggdavison.com.