The proposal for the westward extension of I-66 was started by business interest in Wichita, Kansas. The choice for the number I-66 was a hope to capitalize on the name association with the decommissioned
U.S. Route 66 (US 66). The
Federal Highway Administration (FHWA) originally studied the extension of the existing I-66 in the original Trans America Transportation Corridor Feasibility Study published by Wilber Smith Associates on September 8, 1994. The first version of the Future I-66 Trans America Corridor started from its existing western terminus at I-81 near
Middletown, Virginia, across the nation to California. One concept was to terminate near Fresno, the other Los Angeles. Either way required expensive excavation and tunneling through the Rockies and the Sierra Nevadas to reach Fresno or through Death Valley National Park to reach Los Angeles. The route west of Kansas was not favored by any of the related state highway departments, and, as a result, I-66 west of Wichita, through New Mexico, Arizona, and California was canceled because of lack of interest from any of the state highway departments, and the insufficient projected traffic versus the extreme expense of building through the widest and highest mountains in the nation did not justify an Interstate, especially since many segments had no preexisting highway to reduce environmental damage let alone crossing Death Valley National Park which the National Park Service immediately rejected. Congress decided to create the East-West Trans America High Priority Corridor 3 in the Intermodal Surface Transportation Efficiency Act of 1991, shifting the route south from Washington, DC, to the Norfolk–Chesapeake area, continuing through West Virginia, Kentucky, Illinois, Missouri and terminating at I-35 in Wichita. The
Virginia Department of Transportation (VDOT) studied the conversion of
US 460 to an
Interstate-standard freeway as part of the Trans America Corridor. As proponents wanted all of the Trans America Corridor designated as Future I-66, this required VDOT petition the
American Association of State Highway and Transportation Officials (AASHTO) or Congress to decommission the existing I-66 in North Virginia, changing its designation to an unspecified Interstate number, and designating the conversion of US 460 to Future I-66. The Virginia state legislature was prepared to proceed with the Interstate-standard freeway conversion of US 460. VDOT rejected the conversion once the Trans America feasibility study concluded the nationwide highway was not economical, with little traffic benefit, and I-66 remained as it does today. Congress limited the I-66 designation only to the section of the Trans America Corridor from the then planned I-73/I-74 conversion of the
US 52 (
King Coal Highway) in West Virginia, through Kentucky, Illinois, terminating at I-57 in Missouri. Future I-66 in West Virginia, Kentucky, Illinois, and Missouri would have remained disconnected from the existing I-66. The I-66 concept was supported in Kentucky mainly because of the efforts of Representative
Hal Rogers; however, the Kentucky Transportation Cabinet (KYTC) completed its feasibility study in 2005 and concluded in 2005 that building I-66 was too costly, had little traffic benefit, had no eastern terminus because I-73/I-74 had little chance of completion in West Virginia, and high potential environmental impact in the Daniel Boone National Forest. KYTC made it a low priority wishlist project in the state transportation planning documents and state budget, effectively canceling the project in Kentucky. The only remaining study of I-66 was conducted by the FHWA, the
Illinois Department of Transportation (IDOT) and KYTC under the name "66 Corridor", a Tier 1 environmental impact statement (EIS). This study was canceled on August 6, 2015, by IDOT, and subsequently, the FHWA announced the cancellation of the EIS in the
Federal Register, ending the last I-66 project and therefore officially canceling the I-66 Trans America Highway. Designating the Trans America Corridor as Future I-66 was more nostalgia than logical, a legal requirement for a highway to be included in the Interstate Highway System. Had the proposed Interstate designation been Future I-50 or Future I-60, VDOT would not have needed to change every highway sign on the existing I-66. Although current Federal law does not allow that the same number be used for an Interstate Route and a U.S. Route in the same state, in this case I-50 and US 50 or I-60 and US 60, Congress is free to designate the Interstate Highway with whatever number it wants by law, like it did with I-69 and US 69 in Texas. Business and local political interests in Cape Girardeau, Missouri, is the only public group still advocating the "I-66 Trans America Corridor", but there are no plans in the FHWA to fund their concept after the FHWA cancelled any further studies of I-66 in 2015. Congress has the option to revive the Trans America Corridor, following a less environmentally damaging route like US 50 through Kansas to I-70 in Grand Junction, Colorado, to provide an alternate freight corridor to I-70 connecting to the Cheasepeake Bay ports in Virginia with higher traffic benefits, designated as Future I-50 or Future I-60 by law. In addition, AASHTO has the authority to decommission the same number from the U.S. Route, allowing an Interstate Highway to use the same number, as they did by decommissioning US 40 in Northern California to allow I-40 in Southern California. ==Route description==