1789 to 1860

Envisioned by George Washington, US 40, or the National Road was built to connect the East and West. Needed by farmers and emigrants alike, the National Road would provide a stable route for trade through the Allegheny Mountains.^[4] The National Road was preceded by buffalo trails, Native American footpaths, and the Nemacolin Trail. After the Revolutionary War, and an increase in migration westward, the newly formed national government realized that communication with the west would be difficult with the Appalachian Mountains separating the east coast from the western frontier. Therefore, the highway was put into Ohio's statehood bill by Albert Gallatin in 1802.^[5]

In 1806, Thomas Jefferson authorized the construction of the Cumberland Road—the first federally funded highway in American history. Construction began in 1811 in Cumberland, Maryland and was completed to Wheeling, Virginia (present-day West Virginia) in 1820. In the 1830s, possession of the highway was turned over to the states through which it passes, which allowed states to collect tolls. The Commonwealth of Pennsylvania constructed six tollhouses along its 90–mile–segment of the highway. Two of these still stand: the Petersburg Tollhouse in Addison and the Searights Tollhouse in Fayette County. The Petersburg Tollhouse is the last remaining tollhouse constructed of native-cut stone in the United States.^[6][7] Mile markers were also placed along the route. Made of cast-iron, these obelisk markers were placed every one mile and noted the distance to Cumberland and Wheeling and nearby towns. All of these markers are present today, though not all are the originals. Also in the 1830s, the Pony Express utilized the National Road. The 1840s marked the peak of the National Road. Used by many important figures including presidents, future presidents, and other notables, local businesses saw booming success along the road. This time period gave the National Road its nickname of the nation's "Main Street". The navigation of the Monongahela River after the construction of several locks and dams gave the National Road access to Pittsburgh via Brownsville. The Baltimore and Ohio Railroad also arrived in Cumberland in the 1840s. This allowed travel from the east coast to Cumberland via train, from Cumberland to Brownsville via stage coach, and then from Brownsville to Pittsburgh via steamboat. In the 1850s, railroads made it to the west causing the demise of the National Road.^[5]

1860 to present

In the 1860s, the National Road became insignificant due to the use of the railroads. Many businesses along the route became private homes and the stage coach line went out of business. States relinquished responsibility of the highway to the counties so little or no maintenance was performed on the road. The 1880s brought a small revival to the National Road with the formation of the Good Roads Movement. The invention of the automobile would truly revitalize the highway. Touring along the National Road was popular and many of the businesses returned to offer services to this new type of consumer. The Post Office Appropriation Act of 1912 and the Rural Road Act of 1916 provided funds to rebuild the National Road, and World War I and the overburdened railroads made national highways a priority in the early twentieth century. In 1921, the National Road became U.S. Route 40 after the National Highway Act. The Pennsylvania Route 11 designation was also given to the National Road through Pennsylvania, eventually becoming Pennsylvania Route 81 before the road became solely US 40. The road became very popular again in the 1940s, but this only lasted until the 1950s when the Interstate Highway System was put into place. Today, US 40 has been replaced significantly by Interstate 70 and Interstate 68. US 40 is still used as a local road and scenic route in Pennsylvania, however. US 40 in Pennsylvania has been designated an All American Road (June 13, 2002), a Pennsylvania State Scenic Byway (July 11, 1996), and the Pennsylvania Heritage Corridor (May, 1994).^[4][5]