Oklahoma State Highway 4 Oklahoma State Highway 4 State Highway 4, abbreviated as SH-4 or OK-4, is a designation for two distinct highways maintained by the U.S. state of Oklahoma. One of them serves as an important route through the suburbs west of Oklahoma City, while the other connects US-259 to the Arkansas state line west of Cove, Arkansas. SH-4 has no lettered spur routes. The two SH-4s were never connected. The Central Oklahoma highway was established in 1941 and gradually extended to its present extent between then and 2003. The Eastern Oklahoma highway was originally numbered SH-21, and was renumbered to SH-4 in
Oklahoma State Highway 51 Oklahoma State Highway 51 State Highway 51, abbreviated to SH-51 or OK-51, is a major state highway in Oklahoma. It runs for 333 miles (535½ km) east–west across the state, running from the Texas state line to Arkansas. It is the third-longest state highway in the system. 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. 11 miles (18 km) after