State Highway 66 (abbreviated SH-66) is a state highway in the U.S. state of Oklahoma, beginning at U.S. Highway 81 in El Reno and ending at U.S. Highway 60 near White Oak. The highway was designated in 1985 as a replacement for the decommissioned US 66. Although most of the highway follows Historic Route 66, the highway follows US 66's final alignment, joining Interstate 44 through Tulsa and Oklahoma City, while older versions of the route follow various city streets through both cities. The highway has retained its importance for most of its length due to its paralleling Interstate 44 which between Missouri and Oklahoma City (except in the cities of Tulsa and Oklahoma City) is a toll road. SH-66 currently has one spur route, designated SH-66B, in Wellston. Route description Western terminus and Oklahoma City area State Highway 66 begins at Business I-40 in El Reno (another old Route 66 segment), concurrent at this point with US-81. From this intersection, the highway heads due east. The highway briefly passes through a rural area after leaving El Reno, before transitioning into the Oklahoma City suburb of Yukon. In Yukon, the route runs along Main Street, and has a short concurrency with SH-4. SH-66 continues east, passing into Oklahoma City, where it becomes N.W. 39th Expressway. SH-66 has an interchange with the Kilpatrick Turnpike on the far west edge of the city. The highway passes just to the north of Lake Overholser. Near where the road crosses over the North Canadian River, the inlet to the lake, it crosses from Canadian County into Oklahoma County. N.W. 39th Expressway, still carrying SH-66, forms the main street of both Bethany and Warr Acres, two enclave suburbs of Oklahoma City. The street passes just to the south of Wiley Post Airport and provides access to Southern Nazarene University. After leaving Warr Acres, the highway re-enters Oklahoma City. SH-66 leaves N.W. 39th Expressway at an interchange with I-44 and SH-3/SH-74 (the Lake Hefner Parkway). SH-66 begins a concurrency with eastbound I-44, and for the remainder of its length, it will stay close to the interstate. SH-66 is unsigned through its time on the Oklahoma City freeway system. I-44, while concurrent with SH-66, runs along the north side of Oklahoma City, passing just south of Penn Square Mall, and meets Interstate 235 at a cloverleaf interchange at its northern terminus (north of the interchange, US-77 continues