Interstate 476

Interstate 476 (I-476) is a 132.10-mile (212.59 km) auxiliary Interstate Highway in the U.S. state of Pennsylvania designated between Interstate 95 near Chester and Interstate 81 near Scranton, serving as the primary north–south Interstate corridor through eastern Pennsylvania. It consists of both the 20 mile Mid-County Expressway, locally referred to as the "Blue Route" (although no signs exist with that designation), through the suburban Philadelphia counties of Delaware and Montgomery, and the 110.6 mile Northeast Extension of the Pennsylvania Turnpike connecting the Philadelphia metropolitan area with the Lehigh Valley, the Poconos, and the Wyoming Valley. The Blue Route passes through suburban areas, while the Northeast Extension predominantly runs through rural areas of mountains and farmland, with development closer to Philadelphia and in the Lehigh Valley and the Wyoming Valley. I-476 intersects many major roads including Interstate 76 (the Schuylkill Expressway) in West Conshohocken, Interstate 276 in Plymouth Meeting, U.S. Route 22 near Allentown, and Interstate 80 near Hickory Run State Park.

While proposed as early as 1929, the construction of the Mid-County Expressway through did not begin until 1967 and was not completed until 1991 due to massive community and environmental opposition during the freeway revolts of the 1960s and 1970s, leading The Philadelphia Inquirer to dub it "the most costly, most bitterly opposed highway in Pennsylvania history." In order to get the route through Delaware County built, it was built with many environmental compromises such as a parkway design and four lanes south of the Pennsylvania Route 3 interchange. The Mid-County Expressway received its "Blue Route" nickname from the chosen route through Delaware County on planning maps on which it was differentiated from the other proposed routes by its color. Following the completion of the Mid-County Expressway, in 1996 the Interstate 476 designation was extended to include the entire length of the existing Northeast Extension, replacing PA 9. The Northeast Extension was built between 1955 and 1957 and was originally projected to continue past Clarks Summit to the New York border; however, I-81 was built between these two points instead. Since the extension, I-476 has been the longest auxiliary Interstate Highway in the United States. In addition, I-476 is longer than some main-line interstates such as Interstate 83 in Maryland and Pennsylvania, Interstate 99 in Pennsylvania, Interstate 19 in Arizona and Interstate 97 in Maryland. Additionally, its numbering is unusual since auxiliary interstates beginning in even numbers are typically bypasses rather than spurs.