In a volume subtitled ``The Story of the Pony Express,'' Harness (The Amazing Impossible Erie Canal, 1995, etc.) traces the exuberance and the debt that—for a brief period in 186061- -blazed the mail west in ten short days, half the time it had taken by stagecoach. The historical context is planted around the venture: the rumblings of civil war, Lincoln's pending election, the upheaval of native lands as more settlers pressed westward. Harness also dwells on the youth and instincts of the riders, who battled weather and fatigue, and provides factual asides that can be pored over once the main story is known, e.g., a list of 182 names of riders (the last died in 1955, in New York City). When paired with Andrew Glass's The Sweetwater Run (p. 1399), about Bill Cody's stint with the Pony Express, this book will be ideal for units on the West, for it makes historical events fairly roar with immediacy. (Picture book/nonfiction. 7-10)