Oklahoma State Highway 51

SH-51 meets many different highways in Seiling

SH-51 begins at the Texas line concurrent with US-60 just east of Higgins, Texas. It remains concurrent for 61 miles (98 km) until it reaches US-270/US-281/SH-3 at Seiling, Oklahoma. At Seiling, SH-51 joins with those three highways for nine miles (14 km) before splitting off on its own.

Eleven miles (18 km) after splitting off, Highway 51 meets SH-58 in Canton. It then continues east, crossing the North Canadian River and meeting SH-51A before turning northeast toward Okeene, where it intersects SH-8. SH-51 will go for 24 miles (39 km) before intersecting another highway.

In Hennessey SH-51 meets US-81 before continuing eastward. Seventeen miles (27 km) later, it meets SH-74 north of Crescent. Eleven miles (18 km) to the east, it shares a brief concurrency with US-77; Two miles (3.2 km) later it has an interchange at Interstate 35 at Exit 174.

After crossing I-35, SH-51 becomes a multilane highway and a major corridor linking I-35 to Stillwater, the home of Oklahoma State University. Along this 13-mile (21 km) stretch is an intersection with SH-86. When SH-51 reaches Stillwater, it meets US-177.

Continuing east from Stillwater, the road returns to a two-lane highway after sharing a 1-mile (1.6 km) concurrency with SH-108 and intersects with SH-18 Eight miles (13 km) later. Four miles (6.4 km) east of this, it passes through Yale, Oklahoma before crossing SH-99. It becomes a multilane highway again after SH-48. It turns into the "Mannford Freeway" before passing through the small towns of Mannford and Lotsee on its way toward the Tulsa area.

In Sand Springs, SH-51 crosses the Arkansas River with SH-97 before merging onto the Sand Springs Expressway (US-412/US-64). When this freeway ends at I-244 near downtown Tulsa, SH-51 merges onto I-244 southbound only to exit 1 mile (1.6 km) later, where it runs concurrent with US-64/US-75. This freeway is actually Interstate 444, but the route is not signed as such. After one more mile, SH-51 leaves the interstate with US-64 and becomes the Broken Arrow Expressway, a freeway running northwest–southeast through Tulsa which is known as "The BA" by locals and local media. US-64 leaves the freeway as a concurrency with US-169 southbound. Later, SH-51 will exit the freeway and become a four-lane highway toward Coweta. The mainline freeway becomes the Muskogee Turnpike.

At Coweta, SH-51 turns back east after heading southeast through the Tulsa area. After crossing the Muskogee Turnpike again and bridging the Verdigris River the highway soon enters Wagoner, where it junctions with US-69. Returning once again to a 2-lane road, Highway 51 crosses Ft. Gibson Lake and the town of Hulbert. Eleven miles (18 km) later, it passes through Tahlequah, where it has a brief concurrency with US-62/SH-10. After spitting with these highways, it heads southeast toward Stilwell, Oklahoma, running concurrent with US-59 for a mile on the way. After leaving Stilwell it provides access to Adair State Park, and then crosses the Arkansas line becoming Arkansas Highway 244, which quickly connects to Arkansas Highway 59.