- Southern Terminus:
- West Virginia-Virginia state line
- Northern Terminus:
- Virginia-Maryland state line
- 0.57 miles
US 340 is a north/south route extending from Greenville, Virginia, to Frederick, Maryland. After passing through the eastern panhandle of West Virginia, it re-enters Virginia for a very short distance before crossing the Potomac River to Maryland. This northern section, only about half a mile long, is known as Jefferson Pike and has a single intersection before leaving the state again.