List of Interstate Highways
There are 70 primary Interstate Highways in the Interstate Highway System, a network of controlled-access freeways in the United States. They are assigned one- or two-digit route numbers, whereas their associated "auxiliary" Interstate Highways receive three-digit route numbers. Typically, odd-numbered Interstates run south-north, with lower numbers in the west and higher numbers in the east; even-numbered Interstates run west-east, with lower numbers in the south and higher numbers in the north. Highways whose route numbers are divisible by "5" usually represent major coast-to-coast or border-to-border routes (ex. I-10 travels from Santa Monica, California, to Jacksonville, Florida, traveling from the Pacific to Atlantic oceans). Additionally, auxiliary highways have their numbering system where a different number prefixes the number of its parent highway.
U.S. Route 50
U.S. Route 50 (US 50) is a major east–west route of the U.S. Highway system, stretching just over from West Sacramento, California, to Ocean City, Maryland, on the Atlantic Ocean. Until 1972, when it was replaced by Interstate Highways west of the Sacramento area, it extended (by way of Stockton, the Altamont Pass, and the Bay Bridge) to San Francisco, near the Pacific Ocean. The Interstates were constructed later and are mostly separate from this route. It generally serves a corridor south of Interstates 70 and 80 and north of Interstates 64 and 40. The route runs through mostly rural desert and mountains in the Western United States, with the section through Nevada known as "The Loneliest Road in America". In the Midwest, US 50 continues through mostly rural areas of farms as well as a few large cities including Kansas City, Missouri; St. Louis, Missouri; and Cincinnati, Ohio. The route continues into the Eastern United States, where it passes through the Appalachian Mountains in West Virginia before heading through Washington, D.C. From there, US 50 continues through Maryland as a high-speed road to Ocean City. Signs at each end give the length as , but the actual distance is slightly less, due to realignments since the former figure was measured. US 50 passes through a total of 12 states; California, Nevada, Utah, Colorado, Kansas, Missouri, Illinois, Indiana, Ohio, West Virginia, Virginia, and Maryland, as well as the District of Columbia.