Predecessors and planning in
Kingman, Arizona During the
colonial and
westward expansion eras, a number of
Native American trails existed within the vicinity of what is now Interstate 40. In 1857, an expedition led by Lt.
Edward Fitzgerald Beale was tasked with establishing a trade route along the
35th parallel north from
Fort Smith, Arkansas, to
Los Angeles, California. This route, which became known as
Beale's Wagon Road, was constructed by a team of about 100 men and 22 camels led by Beale. Completed in 1859, it is generally considered the first federal highway in the Southwestern United States. In the early 20th century, a number of
auto trails were established by private organizations to aid motorists in traveling between major cities. Among these was the
National Old Trails Road, which roughly followed the western part of present-day I-40 to Albuquerque, and the
Lee Highway, which followed much of the eastern portion of the route. When the state governments established the
United States Numbered Highway System in 1926, two of these most important highways,
US 66 and
US 70 were established within the present-day I-40 corridor. US 66, which followed the route from its western terminus to Oklahoma City, became arguably the most famous highway in the United States and has been recognized multiple times in popular culture. US 70, which roughly follows the remainder of the Interstate, was also one of the most important highways for east−west travelers, and was considered part of the "Broadway of America" highway between California and
New York. An east−west trans-continental freeway to serve the south-central United States was proposed in multiple plans throughout the 1930s and 1940s for what later became the
Interstate Highway System. The general alignment for the highway that became I-40 was included in a plan released on August 2, 1947, by the Public Roads Administration of the now-defunct
Federal Works Agency. The Interstate was officially authorized between Barstow and Greensboro by the
Federal-Aid Highway Act of 1956, which created the Interstate Highway System. The numbering was subsequently approved by the
American Association of State Highway Officials (AASHO) on August 14, 1957, along with most of the system. The California state government also submitted
State Route 58 (SR 58) between
Barstow and
Bakersfield for I-40 extension potential in 1956 and 1968, but both of these requests were rejected. From 1963 to 1966, the US government considered a plan, part of
Project Plowshare, to use atomic bombs to excavate a path for I-40 through California. The project was canceled largely due to the cost of developing the explosives and due to the unavailability of a "clean bomb".
Construction The first sections of I-40 reused freeways that had been constructed prior to the Interstate Highway System or were under construction at the time of the authorization of the system. The first stretch in Tennessee reused a short freeway in Knoxville called the Magnolia Avenue Expressway, which was opened in two segments in 1952 and 1955. The first stretches in North Carolina were a short controlled-access section of
US 421 in Winston-Salem, and from
Kernersville, constructed between 1955 and 1958. By 1957, most states had begun construction on the first sections of I-40. The first construction project specifically for I-40 in 1958 was a section along the
Pigeon River in Western North Carolina. The stretch between Memphis and Nashville, completed on July 24, 1966, was the first major stretch of interstate highway completed in Tennessee. On June 30, 1972, the final stretch of I-40 entirely within Arkansas, located between
Clarksville and
Ozark was opened; the last section to open in the state was the
Hernando de Soto Bridge, which opened on August 2, 1973. The last segment in California to be completed was a short stretch in Needles, opened on August 13, 1973. The last original planned stretch of the highway in Tennessee, located east of Knoxville, was partially opened on December 20, 1974, and fully opened on September 12, 1975. The last section of I-40 in Oklahoma, a stretch near
Erick near the western end of the state, opened on June 2, 1975. In 1971, the North Carolina State Highway Commission approved a plan to extend I-40 from
Research Triangle Park to
I-95, a distance of , at a cost of $75 million (equivalent to $ million in ). Most of the highway would be four lanes, though six lanes were likely near
Raleigh, where I-40 would extend the
Beltline. Several routes were being considered, but, at the time, the most likely route would have ended north of
Smithfield. When the last portion of I-40, connecting Wilmington to Raleigh, was dedicated on June 29, 1990, CBS journalist
Charles Kuralt stated:
Controversies In
Memphis, I-40 was originally planned to pass through the city's
Overton Park, a public park. Following a public announcement of the routing, a group of community activists opposed to the routing founded an organization called
Citizens to Preserve Overton Park in 1957, and collected 10,000 signatures in their support. After Secretary of Transportation
John Volpe authorized the state to solicit bids for the construction of the Interstate through the park in 1969, the organization filed a lawsuit, which culminated in the
landmark Supreme Court ruling of
Citizens to Preserve Overton Park v. Volpe in 1971, which ruled that the state highway department had not adequately explored alternative routes for the interstate. This case is considered to have established the modern process of
judicial review of infrastructural projects, and eventually resulted in the state rerouting the alignment of I-40 through the park onto a section of I-240 in 1981.
Major projects Between May 1980 and March 1982, a major project was conducted on I-40 in Knoxville that widened the route, eliminated several interchanges, added frontage roads, and reconstructed the congestion-prone cloverleaf interchange with I-75, which had earned the nickname "Malfunction Junction", into a three-level stack interchange. This was conducted as part of a larger $250 million (equivalent to $ in ) road improvement project in the Knoxville area in preparation for the
1982 World's Fair. Originally, I-40 was constructed through, what eventually became the center of downtown
Winston-Salem, until late 1992. After the new route was completed during the period, I-40 was relocated to the new freeway through the then heavily undeveloped areas south of the congested Downtown. The old highway was then redesignated as
Interstate 40 Business (I-40 Bus.), establishing a business route that was actually a freeway for its entire length, a rarity among business routes. Following the reconstruction in one stretch of the old route, the Business Loop was renamed
Salem Parkway and was redesignated to be the segment of
US 421. The "
Big I" interchange in Albuquerque between I-40 and I-25 was reconstructed between 2000 and 2002 in a project that eliminated left-hand entrance ramps and added lanes. This project was given an honorable mention by the
United States Department of Transportation and the FHWA for excellence in urban highway design in 2002. The
Oklahoma City Crosstown Expressway was relocated and replaced with a new wider alignment in two phases between May 2002 and October 2012. The old alignment was replaced with
Oklahoma City Boulevard, and at-grade thoroughfare. In Memphis, the cancellation of the Overton Park stretch of I-240, along with increased traffic volumes and safety hazards, rendered both interchanges with I-240 unable to effectively handle unplanned traffic patterns, thus necessitating their reconstruction. This was accomplished in three phases between January 2001 and December 2016. A $203.7 million two-phase project dubbed "SmartFix 40" resulted in a complete closure of a short stretch of I-40 through Knoxville between May 1, 2008, and June 12, 2009. This was done in order to accelerate the construction timeline, and during this time, through traffic was required to use
I-640. Both phases of the project won an America's Transportation Award from AASHTO in 2008 and 2010, respectively.
Geological difficulties Landslides are common in the Pigeon River Gorge section along the Tennessee and North Carolina border. Here, the roadway was cut into the slopes of several steep mountains. Accidents on the winding road are also common especially during bad weather. On October 25, 2009, I-40 was closed at the North Carolina and Tennessee border due to a landslide at milemarker 2.6 just east of the Tennessee state line. All traffic was detoured via I-26 and I-81, and non-heavy-load traffic via US 25 and US 70. The roadway was reopened on April 25, 2010, with some remaining limitations on westbound traffic.
Major incidents On December 23, 1988, a
tanker truck hauling liquefied propane
overturned on a ramp in the interchange between I-40 and I-240 in the
Midtown neighborhood of Memphis, rupturing a small hole in the front of the tank. The leaking gas ignited in a massive fireball, and the tank was propelled from the crash site into a nearby duplex apartment. The incident killed six motorists and three occupants of nearby structures, and provided momentum for the eventual reconstruction of the interchange. A subsequent investigation revealed that the crack had existed since at least May 2019, and reports later surfaced that the crack had likely existed since August 2016. An emergency contract to repair the beam was awarded six days after the closure, and the bridge reopened on July 31, 2021, to eastbound traffic, and to westbound traffic on August 2, 2021. The highway was badly damaged during
Hurricane Helene in September 2024, with the road closed in multiple locations across western North Carolina due to landslides. The worst damage was seen near North Carolina's border with Tennessee, where a large portion of the highway was washed into the
Pigeon River following a mudslide, resulting in it being indefinitely closed in both directions. On November 5, it was announced that the highway could reopen as early as the beginning of 2025. ==Major junctions==