US 56 runs concurrent with US 412 for its entire length in New Mexico, and are signed as such through the state. The two routes begin in Springer and head east towards Abbot, where they serve as the northern terminus of State Road 39. Continuing east, US 56/412 meet the southern terminus of NM 193 south of Farley, the northern terminus of NM 120 east of Gladstone, and the southern terminus of NM 453. US 56/412 intersect US 64 and US 87 in Clayton, New Mexico, and US 64 joins with US 56/412 in their trek northeast. The three routes serve as the southern terminus of NM 406 as they enter the Kiowa National Grassland. The three routes then cross into Oklahoma together.
Oklahoma
US-56's short path through Oklahoma consists of a diagonal slice across the western part of the Oklahoma Panhandle. US-56/64/412 enter Oklahoma near the southwest corner of the Panhandle, where they also enter Rita Blanca National Grassland. They leave the grassland near Felt. Three miles southwest of Boise City, US-385 joins the concurrency. The routes then enter Boise City, where they enter a traffic circle around the Cimarron County Courthouse that involves US-56, US-64, US-385, US-412, State Highway 3, and SH-325. After leaving the traffic circle, US-56 overlaps US-64, US-412, and SH-3. east of the courthouse, US-56 meets US-287 at an interchange. US-56/64/412/SH-3 continue northeast for, where US-56 splits to travel northeast on its own. The route parallels the Cimarron Valley Railroad for the remainder of its time in Oklahoma. Keyes is the next town on US-56, and it also serves as the northern terminus of SH-171 where the two highways intersect. US-56 crosses into Texas County east of Sturgis. Just before crossing the Kansas line, US-56 meets the north end of SH-95. US-56 then enters Kansas on the east edge of Elkhart.
For one mile in Kansas City's Country Club Plaza, Route 56 follows the noted boulevard Ward Parkway along with 47th St through the Country Club Plaza. The route ends at an intersection with U.S. Route 71. It also includes Blue Parkway and Swope Parkway at certain points.
History
In the early 1950s, towns along what was then the K-45 corridor, connecting Ellsworth, Kansas to the Oklahoma state line at Elkhart, formed the Mid-Continent Diagonal Highway Association to push for a new highway from Springer, New Mexico northeast across the Oklahoma Panhandle, along K-45, and continuing to Manitowoc, Wisconsin on Lake Michigan. By mid-1954, it was being promoted as U.S. Route 55 between the Great Lakes and the Southwestern United States. The first submissions to the American Association of State Highway Officials to establish the route were made in 1954; all placed the northeast end at Manitowoc, Wisconsin, while they varied on whether the southwest end was to be at Albuquerque, New Mexico or Nogales, Arizona. The first route considered in northeast Kansas was via US 40 from Ellsworth to Topeka and K-4 and US 59 via Atchison to St. Joseph, Missouri. A revised route adopted in March 1955, due to AASHO objections to the original route, which traveled concurrently with other U.S. Highways for over half of its length, followed K-14, K-18, US 24, K-63, K-16, and US 59 via Lincoln and Manhattan. In July, the US 50-N Association proposed a plan that would have eliminated US 50N by routing US 55 along most of its length, from Larned east to Baldwin Junction, and then along US 59 to Lawrence and K-10 to Kansas City; towns on US 50N west of Larned, which would have been bypassed, led a successful fight against this. However, in September of that year, the Kansas Highway Commission accepted that plan, taking US 55 east to Kansas City. On June 27, 1956, the AASHO Route Numbering Committee considered this refined plan for US 55, between Springer, New Mexico and Kansas City, Missouri, with a short US 155 along the remaining portion of US 50N from Larned west to Garden City. The committee approved the request, but since the proposed route was more east–west than north–south, it changed it to an even number – US 56 – and the spur to US 156. US 56 originally took a different route between Boise City, Oklahoma and Elkhart, Kansas. The original route followed US 64 east to an intersection south of Eva. It then split off to the north towards Elkhart. By 1961, the section north of US 64 had been overlaid with SH-95. The following year, US 56 was rerouted over SH-114, bringing it to its current diagonal path across the Oklahoma Panhandle. The old alignment is still on the Oklahoma highway system as the north half of SH-95.
