Mark Twain is the best-known and most-beloved American writer in the world, and his stature as the quintessential American writer rests in large part upon his "westernness." Born at the edge of the frontier, schooled along the great divide between East and West--the Mississippi River--and apprenticed in his craft in Nevada and California, Twain's personality was shaped and his art defined by his western experiences, and even when he wrote works not concerned with the American West, attitudes, methods, and comic devices in his writings bore the unmistakable mark of a western mindset.

In the spring of 1835 John Marshall Clemens and Jane Lampton Clemens loaded up their four children in Tennessee and joined the great migration of the westward movement in nineteenth-century America, heading for fortune and affluence in Missouri, at the edge of the jumping-off point for the frontier. Jane was pregnant with a son who was...