The Cuban flag has been raised over Havana's embassy in Washington for the first time in 54 years as the United States and Cuba formally restore relations.
The diplomatic thaw began with a breakthrough announcement by US President Barack Obama and Cuban President Raul Castro last December.
With the re-establishment of relations severed more than five decades ago, the US Embassy in Havana was also officially reopened for business.
Serious differences remain between the United States and Communist-ruled Cuba, and efforts toward full normalisation of ties are expected to proceed slowly.
But the ceremonies carried enormous symbolism after more than two years of negotiations between governments that had long shunned each other.
Cuban Foreign Minister Bruno Rodriguez presided over the reinauguration of the embassy. A three-man honor guard marched onto the front lawn where the Cuban flag was mounted on a newly installed pole while a band played the Cuban national anthem.
As the flag was slowly raised, there were competing chants from the crowd outside the gates. "Cuba si, embargo no!" Shouted one group. "Cuba si, Fidel no," yelled a much smaller group.
More than 500 people, including Obama administration officials, US lawmakers and a large visiting Cuban delegation, attended the ceremony at the nearly century-old mansion that was being converted back into the Cuban Embassy.
In Havana, the US Embassy was also reopened for business with no outward sign of change. Embassy staff flashed new badges and business cards, and the website, Twitter feed and Facebook page of the mission changed. The Stars and Stripes, however, will not be hoisted there until a visit by US Secretary of State John Kerry expected on 14 August.