Arbigland on the Solway Coast, the home of John Paul Jones, was threatened with closure given a lack of funds.
Now, Jim Poole, 64, of San Diego, has offered the museum, which is near Kirkbean, Kirkudbrightshire, a lifetime financial pledge, worth around £11,500 a year, so it can stay open.
Poole described the cottage where Jones, who is considered to be the ‘father of the US Navy’, as a piece of history that needed to be protected.
Mr Poole, who wed at Arbigland last year, told BBC Scotland: “As I tell people, the museum is a sacred ground of American and Scottish history,” he said.
“To let it disappear would be a crime - we have to keep this for future generations.
“He started off in such humble beginnings and what he went on to accomplish - to become one of the greatest heroes in the history of the United States.
“And this was where it all started.”
The cottage, where Jones lived with his father, a gardener on the Arbigland Estate near Dumfries, was turned into a museum to honour the sailor’s achievements.
Jones learned to sail from the neighbouring village of Carsethorn took his first voyage to America aged just 13.
By 29 he had joined the American, or Continental Navy.
In 1779 he went into battle against the British Navy at the Battle of Flamborough Head off the Yorkshire Coast.
Jones, in command of the Bonhomme Richard, and his men came under heavy fire and he was asked to surrender.
He is said to have replied with ‘I have not yet begun to fight’ and went on to lead the capture of the far superior British frigate Serapis.
He died in France in 1792 and his remains were later buried in the crypt of the US naval academy chapel.