Manassas is about 30 miles southwest of Washington, D.C. By car, take I-66 west and exit at Route 234 south into the city — the drive takes around 45 minutes outside rush hour, considerably longer during peak commuting times.
By rail, Virginia Railway Express (VRE) runs commuter trains from Washington Union Station to Manassas on weekdays. The journey takes about 75 minutes. Amtrak also stops here on the Cardinal line (Chicago–New York), though service is infrequent — three days a week in each direction. There is no practical weekend rail service from D.C., so most visitors coming without a car either rent one or arrange a rideshare from the suburbs.
The nearest major airport is Washington Dulles International (IAD), about 25 miles north. Reagan National (DCA) is slightly further but has better transit connections into D.C. if you are combining the trip with time in the capital.