By then, the house had long been lost to foreclosure. After the financial crisis of 2008, Ms. McCauley snatched it off the demolition list for $500. When she met Mr. Mendoza through mutual acquaintances and he expressed interest in shipping the house abroad, she embraced the plan.

“He took the house where he needed to take the house to preserve it,” she said.

Since then, people like the German vice chancellor, Sigmar Gabriel, and the boxing champion George Foreman have made pilgrimages to see it. Ordinary Germans, too, have visited, pleased with the idea that their country is host to a symbol of the American civil rights era.

Now, Mr. Mendoza is looking to America to reclaim the house.

The linchpin of the plan fell into place once the Nash foundation pledged about $45,000 for the trip back home. Mr. Nash said he had learned of the house’s odyssey in an article by The New York Times and emailed Mr. Mendoza in June to ask how he could help.

“Rosa Parks has always been a hero to me,” he said by phone. “And as I learned more about this, my admiration and respect has gown.”

But where should the house spend its third life?

“Should this house go on the lawn of the White House for all time?” Mr. Mendoza asked. “Yes, why don’t we start with the house that was built by the slaves of this country.”

Mr. Nash, a former professor of moral theology at the Catholic University of America in Washington, is partial to relocating it to the capital, where he lives. “My dream is to have it at the new African-American museum in D.C.,” he said.