Oklahoma State Highway 3

Highway 3 begins at the Colorado state line 19 mi (31 km) north of Boise City, Oklahoma. At this terminus, it is concurrent with US-287/US-385. It remains concurrent with the two U.S. Routes until reaching Boise City, where it encounters a traffic circle which contains five other highways. After the circle, US-385 splits off, and SH-3 overlaps US-287, US-56, US-64, and US-412, though US-56 and US-287 both split off within the next 8 miles (13 km).

In Guymon, US-64 splits off. At Elmwood, US-270 joins US-412, coming from a concurrency with State Highway 23. SH-3 remains concurrent with US-270 through Watonga. In Seiling, US-183 leaves the concurrency but is quickly replaced by U.S. Highway 281. SH-33 joins the roadbed 20 miles (32 km) later.

SH-3 and SH-33 concurrency between Watonga and Kingfisher.

In Watonga, SH-33 and SH-3 split off from US-270 and US-281. Highways 3 and 33 remain concurrent for 28 more miles, until Kingfisher, where SH-3 joins U.S. Highway 81. It will stay concurrent with US-81 for 13 miles (21 km), through the town of Okarche. Three miles after Okarche, SH-3 leaves US-81. This marks the first point that SH-3 has not been part of a concurrency.

Beginning at the split from US-81, Highway 3 becomes a major artery in the Oklahoma City highway system, commonly known as the Northwest Expressway because it is a diagonal route and because it serves the northwestern part of the metro area. It skirts the northern limits of El Reno before entering the Oklahoma City limits. The often-congested Northwest Expressway passes through the suburb of Warr Acres and passes close to Lake Hefner.

At the intersection with the Lake Hefner Parkway, SH-3 again re-enters a concurrency. The Lake Hefner Parkway ends very shortly after, and SH-3 becomes concurrent with Interstate 44 through the western side of the city. Near Will Rogers World Airport, Highway 3 transfers to I-240 along the southern side of the city. After I-240 ends, SH-3 is transferred onto I-40 (also carrying US-270), which it remains concurrent with for 16 miles (26 km).

In Shawnee, SH-3 splits into two highways, SH-3E and SH-3W. SH-3W splits off I-40 onto U.S. Highway 177, along with US-270, at I-40 milemarker 181. It continues along with US-270 and 177 through the west side of Shawnee, and continues south of that city until Tecumseh, where US-270 splits off. South of Asher, Oklahoma, SH-3W leaves US-177 and veers southeast toward Ada.

SH-3E, the longer of the two split routes, was the original routing of Highway 3 before the two highways were split. It remains on I-40 for five miles (8 km) after SH-3W splits off. When it does split off, it soon joins SH-18. It follows a route closer to the center of Shawnee. After leaving Shawnee, it heads southeast toward Seminole. Here, it meets US-377/SH-99. SH-3E merges onto this highway, and they will remain concurrent until after they reach Ada.

In Ada, SH-3E and SH-3W are reunited and become SH-3 once again.

SH-3 intersects US 69/US 75, SH-7, and Bypass SH-3 in Atoka.

SH-3 then becomes part of the Richardson Loop, a freeway around the west and south sides of Ada. Throughout the Richardson Loop, it overlaps SH-1 and US-377/SH-99 at different times. The highway then becomes two-lane once again and heads southeast to the town of Coalgate, where begins an 18-mile (29 km) concurrency with U.S. Highway 75, lasting through Atoka. In Atoka, US-75 splits off to join U.S. Highway 69.

Two miles west of Antlers, the highway has an interchange with the Indian Nation Turnpike, and in Antlers it intersects U.S. Highway 271. After reaching the town of Broken Bow, Oklahoma, it turns southward and overlaps US-259 and US-70.

Near Idabel, the highway splits off after being with US-259 for 13 mi (21 km). Twenty-eight miles later, it becomes Highway 32 as it crosses the state line into Arkansas.