Interstate 840 (I-840), formerly State Route 840 (SR 840), is a freeway that serves as an outer bypass route around Nashville, Tennessee. Built by the Tennessee Department of Transportation (TDOT), it is also designated as Tennessee National Guard Parkway. At 77.28 miles (124.37 km) long, it is the tenth-longest auxiliary Interstate Highway in the nation. The route serves the cities of Lebanon, Murfreesboro, Franklin, and Dickson, all suburbs of Nashville.