US40

US40 refers to the **United States Route 40**, a historic east–west highway that once spanned the contiguous United States from New York City to San Francisco. Originally designated as part of the **National Old Trails Road** system in the 1920s, it was later incorporated into the U.S. Highway system as one of the original numbered routes in 1926. The route was nicknamed the **"National Old Trails Road"** or **"Pacific Highway"** due to its alignment along early migration trails, including the **National Road** (U.S. 40’s eastern segment) and the **California Trail**.

US40 followed a roughly 3,000-mile (4,800 km) path through 13 states, connecting major cities such as Baltimore, Pittsburgh, Columbus, Indianapolis, St. Louis, Kansas City, Denver, Salt Lake City, and Sacramento. It was a vital thoroughfare for settlers, travelers, and commerce during the 19th and early 20th centuries, facilitating westward expansion. The highway also served as a key route for military movements, including during World War II.

By the mid-20th century, the rise of the interstate highway system led to the gradual decommissioning of US40. In 1977, the route was officially removed from the U.S. Highway system, though remnants of its alignment persist in some states. Today, portions of the original US40 are preserved as scenic byways, historic trails, or state highways, particularly in the Midwest and West. Notable surviving segments include parts of the **National Road** in Maryland and Pennsylvania and sections in Colorado and Utah that follow historic wagon trails.

US40 holds cultural significance as a symbol of American pioneer spirit and early transportation history. It has been featured in literature, film, and roadside memorials, reflecting its legacy as a defining route of westward migration. While no longer an official highway, its historical importance continues to be recognized through preservation efforts and tourism initiatives.