U.S. Route 23 in Tennessee

U.S. Route 23 (US 23) is a part of the United States Numbered Highway System that travels from Jacksonville, Florida, to Mackinaw City, Michigan. In the U.S. state of Tennessee, the highway travels 57.48 miles (92.51 km) in the northeastern part of the state from the North Carolina state line at Sam's Gap in the Bald Mountains to the Virginia state line in Kingsport. The entire route in Tennessee is a four-lane controlled-access highway and is concurrent with Interstate 26 (I-26) for most of its length. The freeway is also designated the James H. Quillen Parkway for its entire length in Tennessee. US 23 in Tennessee is part of Corridor B of the Appalachian Development Highway System (ADHS) and serves as a major thoroughfare in the Tri-Cities region of the state. Although I-26 is technically an east–west route, the highway predominantly travels in a north–south alignment in the state. The highway reaches a maximum elevation of 3,760 feet (1,150 m) at the North Carolina state line, which is the highest elevation on the Interstate Highway System east of the Mississippi River.

US 23 was first established in Tennessee in 1930 following State Route 36 (SR 36), and paving of the route was completed the following year. The freeway was first authorized by the Appalachian Regional Development Act of 1965, and the stretch between Johnson City and the Virginia state line was constructed in segments between 1968 and 1986. In addition to US 23, this freeway was designated as State Route 137 (SR 137) and later Interstate 181 (I-181) and was commonly referred to as "Appalachian Highway" in its early years. In 1988, the American Association of State Highway and Transportation Officials (AASHTO) approved an extension of I-26 from Asheville, North Carolina, to I-81 in Tennessee. The remainder of the freeway was completed in 1995, and the stretch between the North Carolina state line and I-81 was redesignated as I-26 in 2003. After an initial denial, I-26 was extended north to Kingsport in 2007, replacing the remainder of I-181. Today, the mountainous stretch near the North Carolina state line is widely considered to be one of the most scenic stretches of Interstate Highway in the Eastern U.S.