Ford, until 2006 the weakest of the "big three" Detroit car makers, was able to stay afloat thanks to the loans, while rivals General Motors and Chrysler went bankrupt and had to be rescued by the US taxpayer.
Ford never stopped using the blue oval logo, or any of the other assets it pledged, which included factories and the trademarks of its F-150 pick-up truck and Mustang sports car, but the risks of losing them weighed heavily on the company as it sought cost cuts to restore the business to health, said chairman Bill Ford.
"This is one of the best days that I can remember," he said.
"This is enormously emotional for me personally and for my family."
Bill Ford is the great-grandson of Henry Ford, who founded the company and approved the logo's first versions.
Bruce Clark, senior vice president at Moody's, said: "The key factor in our considering an investment-grade rating for Ford was whether or not the company would be able to sustain its strong performance. We concluded the improvements Ford has made are likely to be lasting."
Ford's European arm has slipped back into the red but in North America it has slashed production to profitable levels.
- Independent