Horse-drawn covered freight wagon.
It originated in the 18th century in the Conestoga Creek region of Pennsylvania. It had a flat body and low sides; with its floor curved up at each end to prevent freight from shifting, it was well suited for travel over early American roads. It became famous as later adapted by westward-traveling pioneers for hauling their possessions; with its tall white canvas top, it resembled a sailing ship from a distance, which earned it the name "prairie schooner."
Conestoga wagon
Encyclopædia Britannica, Inc.