Now the years of neglect - on both counts - are being addressed, in part thanks to a $28 million renovation project.
But not without a few diplomatic challenges along the way according to Benjamin Ziff, the top U.S. diplomat in Cuba.
"This was complicated as well by the Cuban visa policy which was a single-entry visa, so technicians or contractors coming in, if he or she broke a saw blade they'd have to return to the United States to procure another saw blade and then apply for a new visa which could take two months. So, you could see how difficult this process was, even when you could bring people in."
Some of those issues have now been resolved - particularly around worker visas - to be replaced by others.
But Ziff still sees the refurb as critical investment in U.S. diplomacy on the island.
"The important thing to realize about diplomacy is that is not only policy, it's logistics. You need to have a presence; you'd have people you need to have a building you need to have an installation to be able to do diplomacy effectively, and we are on the Malecon, we are in front of the sea which has its own effects on the building."
Former Cuban leader Fidel Castro, often alleged the embassy was a hotbed of spies aiming to overthrow his government.
That was not the motivation when it was built in 1953 in the wake of World War Two, according to architectural historian Jane Loeffler.
"There was great enthusiasm for the United Nations building in New York and the idea of what it symbolized and it happens that the architects for that building were (Wallace) Harrison and (Max) Abramovitz and they were the same architects who went on to design Havana and Rio for the State Department. And this was the impetus for this program and Havana was just one of the very first buildings that the State Department built."
The building operated for years as the "U.S. Interests Section," before reopening as an embassy in July 2015 when diplomatic relations were restored under Barack Obama.
But its staffing was cut sharply two years later after staff began to report a mysterious ailment dubbed "Havana Syndrome."
The Cuban government did not respond to a request for comment to this story, but some Havana residents have applauded the embassy overhaul.
"I work in front of the embassy. I have seen part of the restoration process they have done, inside and out. I think it is important because this is one of the most important embassies in our country. Many Cubans visit it so we can leave, to travel abroad. I think it needs to look good so it's in perfect conditions when it's my turn to visit it."
