prairie schooner

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. A covered wagon, drawn by horses or oxen, that was used by pioneers in crossing the North American prairies and plains.

Wiktionary

1. n. A horse-drawn wagon used to transport people and goods in the American west of the 18th and 19th centuries.

WordNet 3.0

1. n. a large wagon with broad wheels and an arched canvas top; used by the United States pioneers to cross the prairies in the 19th century