The U.S. Capitol Gatehouses and Gateposts — designed circa 1827 by celebrated architect Charles Bulfinch — originally stood on the grounds of the United States Capitol in Washington, D.C. Two of the gatehouses are listed on the National Register of Historic Places in their new locations.
One gatehouse and three of the gateposts now stand at 15th Street and Constitution Avenue within the President's Park South historic district north of the National Mall. The other gatehouse is at 17th and Constitution, also within the PPS. Four other gateposts have been relocated to the main entrance of the National Arboretum at New York Avenue NE and Springhouse Road NE.
Wikipedia https://en.wikipedia.org/wiki/U.S._Capitol_Gatehouses_and_Gateposts
Address 196 17th St NW, Washington 20006, United States
Coordinates 38°53'32.572" N -77°2'21.386" E