US-266 begins at US-62/US-75 on the northeast side of Henryetta, approximately north of Interstate 40. The highway heads east from this point, quickly crossing into the town of Dewar, which it bisects. As it leaves Dewar, US-266 turns northeast, crossing Coal Creek and the Deep Fork River. The highway bypasses Hoffman to the east, providing access via Hoffman Road. The route then passes through the southeastern outskirts of Grayson. The highway then turns due east. Immediately after the curve, the highway serves as the southern terminus of SH-52's northern section. US-266 then continues east into McIntosh County. US-266 continues due east, running parallel to the Deep Fork Arm of Eufaula Lake, the reservoir's northernmost arm. South of Council Hill, the highway intersects SH-72 at its southern terminus. US-266 turns south-southeast, continuing the alignment of SH-72. The route then turns back to the east and heads into the city ofChecotah. On the west side of town, US-266 has an interchange with the modern freeway route of US-69. Further east, in downtown Checotah, the route intersects the old alignment of US-69, US-69 Business. The highway heads due east out of Checotah, descending a ridge and passing just south of its summit, Mt. Nebo. The highway passes under Interstate 40 just before crossing into Muskogee County. Just under east of the McIntosh–Muskogee county line, US-266 intersects the southern SH-2. US-266 begins a concurrency with the state route, traveling northwest to an interchange with I-40, numbered as Exit 278. The highways then curve around to due north to pass through Warner. On the north edge of Warner lies an intersection with US-64, where both US-266 and SH-2 end. Continuing straight puts the traveler on westbound US-64 bound for Tulsa, while turning right brings the motorist onto eastbound US-64 toward Fort Smith, Arkansas.
History
Prior to the inception of the U.S. highway system, SH-9 covered much of the corridor from Oklahoma City to Spiro. Upon the US route system's inception, US-266 replaced SH-9 from its junction with US-66 at 23rd Street and Lincoln Boulevard in Oklahoma City to US-64 in Warner. By 1930, along with changes to several other branches of US-66, the route was truncated at Henryetta. The segment from Oklahoma City to Henryetta became part of U.S. Highway 62, which was commissioned in 1930.