 It was named after James Wilmer Dallam, the lawyer who made the first digest of Texas laws.The first settlement in the area followed in 1870, which resulted in the Red River War of 1874 and 1875 with the native Comanche and Kiowa tribes.In 1900–01, the Chicago, Rock Island and Pacific Railroad company built a stretch from Liberal, Kansas to Tucumcari, New Mexico, which ran through the county.