Oklahoma State Highway 270 1979, US-270 ran through Oklahoma City on surface streets. It left the city and ran through Choctaw concurrent with US-62. US-270 split away from US-62 in Harrah, and continued on to Shawnee on what is now SH-270. On March 5, 1979, US-270 was rerouted to run concurrent with Interstate 40 from south of Calumet in Canadian County through the Oklahoma City metro, exiting the Interstate onto a surface alignment in Shawnee. Presumably, SH-270 was commissioned the same date. The realignment of US-270, with SH-270 on the old alignment between Harrah and Shawnee, appears on the 1979 state map. SH-270 followed
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