Get breaking news alerts and special reports. The news and stories that matter, delivered weekday mornings.

The American flag was hoisted Friday over the U.S. Embassy in Cuba for the first time in more than half a century, marking the end of a Cold War-era diplomatic freeze between two countries 90 miles apart.

“We are gathered here because our leaders made a courageous decision to stop being prisoners of history,” Secretary of State John Kerry declared. He is the highest-ranking U.S. official to visit the communist island since World War II.

"My friends, it doesn’t take a GPS to realize that the road of mutual isolation and estrangement that the United States and Cuba were traveling is not the right one and that the time has come for us to move in a more promising direction," Kerry said. "In the United States, that means recognizing that U.S. policy is not the anvil on which Cuba’s future will be forged."

The ceremony was rich with history: Three of the very Marines who lowered the flag at the Embassy in 1961 were on hand to watch it fly again, Larry Morris, Mike East, and Jim Tracy. Back then, the three men were confronted by a large crowd which parted as the Marines lowered the flag.

"Larry, Mike and Jim had done their jobs, but they also made a bold promise – that one day they would return to Havana and raise the flag again," Kerry said.

Years later, the men returned to fulfill their promise.

"Larry, Jim, Mike. This is your cue to deliver on words that would make any diplomat proud, just as they would any member of the United States Marine Corps: 'Promise made, promise kept',” Kerry told the men as moments later the flag was raised.

Kerry praised both nations' leaders for working to repair the relationship between the two countries.

"I applaud President Obama and President Castro for having the courage to bring us together in the face of considerable opposition," Kerry said.

The Morning Rundown Get a head start on the morning's top stories. This site is protected by recaptcha

Celebrated poet Richard Blanco, who read a composition at Obama's second inauguration, recited a poem entitled "Matters of the Sea."

Related: Kerry and Cuban Foreign Minister Laud Thawed Relations

The historic shift from Cold War era relations was memorialized in July when Cuban officials inaugurated their embassy in Washington.

These Marines have an amazing story. Proud they’ll join me for @USEmbCuba reopening tomorrow. https://t.co/Q97Xs7mmAW pic.twitter.com/PRrT6fLRBG — John Kerry (@JohnKerry) August 13, 2015

Reopening the embassies is an important step toward normalizing relations and economic ties between the two countries after decades of Cold War hostilities. The U.S. severed diplomatic ties with the communist island country in 1961.

Related: Kerry to See U.S. Flag Fly Over Cuba Embassy After 54 Years

President Barack Obama announced in December that the U.S. was ending an "outdated approach" of isolating Cuba. In May, the U.S. dropped Cuba from its list of state sponsors of terrorism.

However, deep ideological differences still divide the two nations.

There are thorny disputes over mutual claims for economic reparations, Cuba's insistence on an end to the 53-year-old trade embargo and American calls for Cuba to improve on human rights and democracy.

Related: Fidel Castro Says U.S. Still Owes Cuba Many Millions of Dollars in Damages

Kerry also acknowledged that hurdles remain.

"We are all aware that, notwithstanding President Obama’s new policy, the overall U.S. embargo on trade with Cuba remains in place and can only be lifted by Congressional action — a step we strongly favor," Kerry said.

Some U.S. lawmakers —including several Republican presidential candidates have staunchly criticized the Obama administration's efforts to thaw relations with Cuba.

"The deal with Cuba threatens America’s moral standing in our hemisphere and around the world, it brings legitimacy to a state sponsor of terror, and further empowers an ally of China and Russia that sits just 90 miles from our shore," Sen. Marco Rubio, R-Florida, who is Cuban American and a GOP presidential hopeful said in a speech at the Foreign Policy Initiative in New York City on Friday.

Kerry was slated to meet later with a number of Cuban dissidents who were not invited to the morning flag-raising in deference to the Cuban government, which views them as U.S.-sponsored mercenaries.

Some see the move as a snub motivated by a U.S. desire to tread carefully as it seeks to improve relations with the Cuban government.

Related: Cuba Dissidents Gather in Puerto Rico as US Embassy Flag Raising Nears

“The accommodation of the Castro regime comes at the expense of the freedom and democracy that all Cubans deserve, but Secretary Kerry’s visit is especially insulting for Cuba’s dissidents," Republican presidential candidate and former Florida governor Jeb Bush said in a statement. "That courageous Cubans whose only crime is to speak out for freedom and democracy will be kept away from the official ceremony opening the U.S. Embassy is yet another concession to the Castros."