<Tr> <Th> Designated NHL </Th> <Td> May 27, 2003 </Td> </Tr> <Tr> <Th> Designated CP </Th> <Td> May 26, 1973 </Td> </Tr> <P> Union Oyster House, open to diners since 1826, is amongst the oldest operating restaurants in the United States of America, and the oldest that has been continuously operating since being opened . It is located at 41--43 Union Street, Boston, Massachusetts . The building was listed as a National Historic Landmark on May 27, 2003 . </P> <P> The building itself was built prior to 1714, most likely in 1704 . Before it became a restaurant, Hopestill Capen's dress goods business occupied the property . In 1771 printer Isaiah Thomas published his newspaper, The Massachusetts Spy, from the second floor . The restaurant originally opened as the Atwood & Bacon Oyster House on August 3, 1826 . </P>

What is the oldest restaurant in the united states