Washington, DC.
The proper noun is spelled Washington (e.g. George Washington, Washington state, Washington, DC).
The US national capital is spelled "Washington DC" (District of Columbia).
Washington dc is not a state.
The likely word is the proper noun Washington City, a location in Utah.(The US national capital is Washington, DC in the District of Columbia.)
Washington, DC
Washington DC
Washington - Baltimore Washington International, DC, USA (BWI) Washington - Washington - All Airports, DC, USA (WAS) Washington - Ronald Reagan National Airport, DC, USA (DCA) Washington - Washington Dulles, DC, USA (IAD)
there are no counties in Washington DC because Washington DC is a city itself.
Washington DC
Washington, DC
On the mall in Washington, DC.