And to Think That I Saw It on Mulberry Street is Theodor Geisel's first children's book. It was published under the pen name Dr. Seuss. First published by Vanguard Press in 1937, the story follows a boy named Marco, who describes a parade of imaginary people and vehicles traveling along a road, Mulberry Street, in an elaborate fantasy story he dreams up to tell his father at the end of his walk.