- Western Terminus:
- Virginia-District of Columbia state line
- Eastern Terminus:
- Whitehurst Freeway (US 29) in Washington
I-66 is an east/west highway connecting Washington to its suburbs and exurbs. It enters the District of Columbia via a bridge over the Potomac River. Less than a mile over the bridge, it ends a the Whitehurst Freeway (US 29).
While it is technically Route 66 because of its I-66 designation, it has no connection to the famed Route 66 of the American West, which is US 66 and doesn't come anywhere near the District of Columbia.