There are three major airports you can use to fly into Washington DC. You can land at the Ronald Reagan Washington National Airport, the Dulles International Airport, or the Baltimore/Washington International-Thurgood Marshall Airport. Most national airlines land into these airports with the exception of Southwest, which only flies into BWI.
Washington DC is a 5-hour flight from San Francisco. If you were coming from New York, it would only take you an hour to get there. From London, it's six hours and 18 hours if you'll fly from Sydney.