Oklahoma State Highway 4

The northern end of SH-4 in Piedmont.

The western Highway 4 is 37.3 miles (60.0 km) long. It begins at the eastern terminus of the H.E. Bailey Turnpike Spur south of Newcastle, Oklahoma. It is a two-lane road until it reaches SH-37, where it expands to four lanes. Seven miles (11 km) later, it joins with SH-152 in the town of Mustang.[4] One mile (1.6 km) later, SH-4 continues northward along Mustang Road toward Interstate 40 and Yukon.[4]

After crossing I-40, SH-4 becomes a two-lane road once again until entering Yukon, at which point it becomes a four-lane road again. It meets SH-66, once Route 66, in Yukon. Seven miles (11 km) later, it meets the Northwest Expressway (SH-3).[4] It lasts for just three miles (4.8 km) longer until ending at Edmond Road in Piedmont.[4]

Just after crossing SH-3, there is a standard distance sign listing Piedmont and "END OF ROUTE", giving the distance to the terminus of SH-4. This is a relative rarity on Oklahoma highways.

The eastern Highway 4 is 12.01 miles (19.33 km) long.[3] It begins at US-259 and goes generally east–west, passing through the unincorporated communities of Smithville and Watson. After crossing the Arkansas state line, it becomes Highway 4.

The western SH-4 was assigned in 1941 to a previously unnumbered roadway between U.S. Highway 66 in Yukon and Piedmont.[1][5] A continuation of SH-4 east to North May Avenue in Oklahoma City along Ranchwood Boulevard and NW 10th Street had been designated as a farm-to-market road four years earlier.[6][7] In 1954, SH-4 was extended eastward along the farm-to-market road to a terminus at State Highway 3 and State Highway 74 (May Avenue) southwest of downtown Oklahoma City.[8][9]

SH-4 remained unchanged until 1979 when it was truncated to its former southern terminus at US-66 in Yukon.[10] The route was then extended to Mustang in 1982, following Ranchwood Boulevard and Mustang Road south to a new terminus at State Highway 152.[11] Construction on a southward extension of SH-4 to State Highway 37 near Tuttle began in 2001[12] and was completed a year later, as was a new segment between SH-37 and the H.E. Bailey Turnpike (Interstate 44).[13] SH-4 was originally signed only as far south as SH-37; the designation was extended south to I-44 in early 2003.

On August 9, 2021, the Oklahoma Transportation Commission voted to approve the addition of the State Highway 4 designation to the H.E. Bailey Spur.

What is now the eastern SH-4 became part of State Highway 21 in 1927 when SH-21 was rerouted north of Bethel to follow modern U.S. Highway 259 and SH-4 to the Arkansas state line.[14][15] The SH-21 designation was removed in 1963 and replaced with SH-4 from Smithville east to the state line near Watson. Only minor realignments, such as the straightening of the roadway near Smithville and the replacement of a historic truss bridge by a modern span have occurred since.[2]

The entire route is in McCurtain County. [16]

Location[16]	mi[3]	km	Destinations	Notes
Smithville	0.00	0.00	US 259	Western terminus
​	12.01	19.33	AR 4 east	Continuation into Arkansas
1.000 mi = 1.609 km; 1.000 km = 0.621 mi