"How many unsafe bridges do you still have here in Ohio? - I mean Iowa – " he said to laughter from the crowd at Abby Finkenauer’s Fish Fry in Cedar Rapids.
He explained that he had just been to Ohio and said they had more unsafe bridges there.
The mistake was just the latest in a series of slip-ups that have plagued Biden throughout his campaign.
Last May, he corrected himself after referring to then-British Prime Minister Theresa May as Margaret Thatcher, who served from 1979 to 1990 and died in 2013. In August, he said how much he loved being in Vermont while he was in New Hampshire.
“I am a gaffe machine, but my God what a wonderful thing compared to a guy who can’t tell the truth,” he said last year.
Biden -- who will turn 77 on Nov. 20 -- has long been known for making gaffes and embellishing stories but the frequency of his misstatements has led some to be concerned about his age.
At the fish fry, Biden touted his support for investments in infrastructure and his pro-union stance.
In an Iowa poll that came out last week, Biden trails in fourth place behind Sen. Elizabeth Warren, D-Mass., who has recently surged, Sen. Bernie Sanders, I-Vt., and South Bend, Ind., Mayor Pete Buttigieg.