The mural along Interstate 95 in Providence was designed by David Macaulay and was completed in June. It's one of two highway murals designed by Macaulay, who attended the Rhode Island School of Design.
Red graffiti covers the length of the mural.
State Department of Transportation spokeswoman Rose Amoros says crews will work through Wednesday to clean it. She says once they remove the paint they'll restore the mural. She calls the vandalism disheartening.
Macaulay has won awards including the Caldecott Medal for children's books. Among his best-known books is "The Way Things Work," an amusing look at the inner workings of everything from cars to computers.