It washed up on a beach at Cape Lookout National Seashore on the Outer Banks in North Carolina last week.
The National Park Service issued a statement last week on Facebook saying it believed the bag had been floating out at sea for 40 years.
“This bag was found last week...on Harkers Island along with other storm debris,” read the post. “The bag design looked odd to us, but we couldn’t put our finger on why until we noticed the date in the lower corner — 1979!”
The photo of the bag included the original Doritos logo as well as the copyright date of 1979.
The discovery showcases how long it can take for plastic to decompose.
“While this was sort of a neat find due to its age, it serves as a reminder that plastic trash lasts a long time, in this case almost 40 years!” the National Park Service said.
Doritos and its parent company, Frito Lay, have not commented on the mystery.