Interstate 40 in Tennessee

Interstate 40 (I-40) is part of the Interstate Highway System that runs 2,556.61 miles (4,114.46 km) from Barstow, California, to Wilmington, North Carolina. The highway crosses the state of Tennessee from west to east, from the Mississippi River at the Arkansas state line to the Blue Ridge Mountains at the North Carolina state line. At 455.28 miles (732.70 km), the Tennessee segment of I-40 is the longest of the eight states through which it passes and the state's longest Interstate Highway.

I-40 passes through Tennessee's three largest cities—Memphis, Nashville, and Knoxville—and serves the Great Smoky Mountains National Park, the most-visited national park in the United States. It crosses all of Tennessee's physiographic regions and Grand Divisions—the Mississippi embayment and Gulf Coastal Plain in West Tennessee, the Highland Rim and Nashville Basin in Middle Tennessee, and the Cumberland Plateau, Cumberland Mountains, Ridge-and-Valley Appalachians, and Blue Ridge Mountains in East Tennessee. Landscapes on the route vary from flat, level plains and swamplands in the west to irregular rolling hills, cavernous limestone bluffs, and deep river gorges in the central part of the state, to plateau tablelands, broad river valleys, narrow mountain passes, and mountain peaks in the east.

The Interstate parallels the older U.S. Route 70 (US 70) corridor for its entire length in the state. It has interchanges and concurrencies with four other mainline Interstate Highways, and has five auxiliary routes: I-140, I-240, I-440, I-640, and I-840. I-40 in Tennessee was mostly complete by the late 1960s, having been constructed in segments. The stretch between Memphis and Nashville, completed in 1966, was the state's first major Interstate segment to be finished. The last planned section was completed in 1975, and much of the route has been widened and reconstructed since then.

The I-40 corridor between Memphis and Nashville is known as Music Highway because it passes through a region which was instrumental in the development of American popular music. In Memphis, the highway is also nationally significant due to a 1971 U.S. Supreme Court case which established the modern process of judicial review of infrastructure projects. Community opposition to the highway's proposed routing through Overton Park led to a nearly-25-year activist campaign which culminated in the case. This resulted in the state abandoning the highway's original alignment and relocating it onto what was originally a section of I-240.

I-40 runs for 455.28 miles (732.70 km) through Tennessee, making it the second-longest stretch of Interstate Highway within a single state east of the Mississippi River. It is the only Interstate Highway to pass through all three of the state's Grand Divisions and all nine physiographic regions. The highway is maintained by the Tennessee Department of Transportation (TDOT). The busiest stretch of highway in Tennessee is on the segment concurrent with I-75 in Knoxville between a connector to US 11/70 and Papermill Road, which had an average daily traffic volume of 218,583 vehicles in 2022. The lowest daily traffic volume that year was 26,985 vehicles at the North Carolina state line. The busiest weigh station in the country is on I-40/I-75 in Farragut, a suburb of Knoxville, which serves more than 2.4 million trucks annually.

I-40 enters Tennessee from Arkansas in a direct east–west alignment via the six-lane Hernando de Soto Bridge, a tied-arch bridge which spans the Mississippi River and has a total length of about 1.8 miles (2.9 km). Entering the city of Memphis (Tennessee's second-largest city), the Interstate crosses the southern half of Mud Island before crossing the Wolf River Harbor and Mississippi Alluvial Plain into Downtown Memphis, where the bridge ends next to the Memphis Pyramid. The highway then intersects US 51 (Danny Thomas Boulevard) and, just beyond this point, abruptly turns 90 degrees north near Midtown at an interchange with the western terminus of I-240, a southern bypass route around the central city. It then intersects SR 14 (Jackson Avenue). Proceeding north, the highway crosses the Wolf River and reaches the eastern terminus of SR 300, a controlled-access connector to US 51. The Interstate then shifts due east, bypassing central Memphis to the north. Passing near the neighborhoods of Frayser and Raleigh, I-40 intersects a number of surface streets and crosses the Wolf River for a second time about five miles (8.0 km) later. It then meets SR 14 again and turns southeast.

A few miles later, I-40 reaches a complex four-level stack interchange with US 64/70/79 (Summer Avenue) and the eastern ends of I-240 and Sam Cooper Boulevard; a pair of overpasses carries its traffic northeast. Entering a straightaway, the Interstate crosses the Wolf River for a third (and final) time; over the next several miles, it passes through the suburban neighborhoods of East Memphis and Cordova and the incorporated suburb of Bartlett in eastern Shelby County. This stretch has eight lanes; the left lanes serve as high-occupancy vehicle (HOV) lanes during rush hour, and it has several interchanges with local thoroughfares. The highway then intersects US 64 and narrows to four lanes. After passing through Lakeland, the Interstate reaches a cloverleaf interchange with the eastern ends of I-269 and SR 385 near the suburb of Arlington.

Leaving the Memphis area, I-40 enters Fayette County east of Arlington; about five miles (8 km) later, it crosses the Loosahatchie River and adjacent wetlands. Over the next 30 miles (50 km), the Interstate crosses a level expanse of farmland and some woodlands and swamplands in a straight alignment, bypassing most cities and communities. An interchange with SR 59 is at exit 35, which provides access to Covington and Somerville. The highway enters Haywood County near the site of Ford Motor Company's Blue Oval City manufacturing facility. Beyond this point, it turns north and enters Hatchie National Wildlife Refuge; the highway crosses the Hatchie River and a number of streams and swamps in a long straightaway. I-40 turns east after the refuge and passes southeast of Brownsville, where it intersects SR 76, SR 19, and US 70. The highway then enters Madison County.