<Li> Searights Tollhouse, near Uniontown, Pennsylvania </Li> <P> Additionally, several mile markers--some well - maintained, others deteriorating, and yet others represented by modern replacements--remain intact along the route . </P> <P> In general, the road climbed westwards along the Amerindian trail known as Chief Nemacolin's Path, once followed and improved by a young George Washington, then also followed by the Braddock Expedition . Using the Cumberland Narrows, its first phase of construction crossed the Allegheny Mountains entered southwestern Pennsylvania, reaching the Allegheny Plateau in Somerset County, Pennsylvania . There, travelers could turn off to Pittsburgh or continue west through Uniontown and reach navigable water, the Monongahela River, at Brownsville, Pennsylvania, which was by then a major outfitting center and riverboat - building emporium . Many settlers boarded boats there to travel down the Ohio and up the Missouri, or elsewhere on the Mississippi watershed . </P> <P> By 1818, travelers could press on, still following Chief Nemacolin's trail across the ford, or taking a ferry to West Brownsville, moving through Washington County, Pennsylvania, and passing into Wheeling, Virginia (now West Virginia), 45 miles (72 km) away on the Ohio River . Subsequent efforts pushed the road across the states of Ohio and Indiana and into the Illinois Territory . The western terminus of the National Road at its greatest extent was at the Kaskaskia River in Vandalia, Illinois, near the intersection of modern U.S. 51 and U.S. 40 . </P>

First national road to span the american continent