They're Off! 
Subtitle: The Story of the Pony Express
Publisher: Aladdin
Published: July 1, 2002
Language: eng
Format: Paperback
Number of pages: 32
ISBN-13: 9780689851216
Subjects: Postal service; Juvenile literature; History; Juvenile Fiction; Children's Books/Ages 4-8 Nonfiction; Children: Grades 3-4; United States; Pony express; History - United States/19th Century; Juvenile Fiction / Historical / United States / 19th Century; Historical - United States - 19th Century
First sentence: In the earliest days of the United States, when the young nation had just broken away from England in the Revolutionary War, the West was the mysterious woods beyond the Appalachian Mountains.