Interstate 81 (I-81) is a major north-south (physically northeast-southwest) Interstate Highway running from I-40 in Dandridge, Tennessee, to the Canadian border on Wellesley Island, New York, where the Thousand Islands Bridge connects it to Ontario's Highway 401. Following ancient animal and settler trails that evolved into US Route 11, it parallels the Appalachian Mountains through states like Virginia, West Virginia, Maryland, and Pennsylvania, passing major cities including Roanoke, Hagerstown, Harrisburg, and Syracuse. Because it is mostly rural and less congested than I-95 to the east, it serves as a vital trucking corridor—but also a route exploited by drug and human traffickers, prompting the FBI to form a taskforce in 2017. The six-state I-81 Corridor Coalition meets annually to tackle issues like truck traffic and air pollution, and the highway offers the fastest route between Washington, D.C. and Ottawa. Notably, Maryland's segment is the shortest of any state (12.08 miles) and was dedicated as the Maryland Veterans Memorial Highway in 1987, while West Virginia's 26-mile stretch was completed in 1966.