Interstate 40 (I-40) is the longest Interstate Highway in Tennessee, stretching from the Mississippi River at the Arkansas border to the Blue Ridge Mountains at the North Carolina border. It passes through the state's three largest cities and serves the Great Smoky Mountains National Park. The landscape on the route varies from flat plains and swamplands to rolling hills and deep river gorges. I-40 parallels the older U.S. Route 70 corridor and has interchanges with four other mainline Interstate Highways. The highway was mostly completed in the late 1960s, with the last section finished in 1975. The I-40 corridor between Memphis and Nashville is known as Music Highway and has historical significance in American popular music. In Memphis, the highway is significant due to a legal case that changed the process of reviewing infrastructure projects. Interstate 40 (I-40) is the second-longest stretch of Interstate Highway in Tennessee, spanning 455.28 miles. It is the only highway to pass through all three of the state's Grand Divisions and nine physiographic regions. Maintained by the Tennessee Department of Transportation (TDOT), the busiest section of the highway is in Knoxville, with an average daily traffic volume of 218,583 vehicles in 2022. The Farragut weigh station on I-40/I-75 serves over 2.4 million trucks annually and is the busiest weigh station in the country. I-40 enters Tennessee from Arkansas via the 1.8-mile Hernando de Soto Bridge. It then crosses Mud Island and the Wolf River Harbor before reaching Downtown Memphis. From there, the highway turns north, bypassing central Memphis, before reaching a complex interchange and continuing through suburban neighborhoods and the suburb of Arlington. Interstate 40 in Tennessee passes through the Gulf coastal plain while bypassing cities and communities. It crosses rivers, wetlands, and woodlands, and intersects with multiple major corridors that connect to different areas in West Tennessee. Eventually, it descends a steep grade into the Western Valley of the Tennessee River, crosses Kentucky Lake, and enters Middle Tennessee. I-40 in Tennessee crosses the Tennessee River into Humphreys County before traversing woodlands in the Western Highland Rim. It then crosses the Buffalo River and Duck River, reaches Dickson County, and crosses the Piney River. It continues through rugged terrain and ascends steeply into Williamson County, passes through Cheatham County and the towns of Kingston Springs and Pegram, and crosses the Harpeth River twice.

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