Before the U.S. Route system, this system of interconnected highway from New Mexico to Oklahoma was part of the Texas highway system and a portion of the Ozark Trails which closely paralleled the Chicago, Rock Island and Pacific Railway. When the United States Numbered Highway system was introduced in 1926, Route 66 across the Texas Panhandle was designated along existing roads in the Texas highway network. The entire route was paved by 1938. There have been various realignments, including one in 1959 to allow expansion of the Amarillo Air Force Base.