Historians Stephen Ambrose and Douglas Brinkley are sailing the Mississippi River aboard the steamboatDelta Queen from New Orleans to Memphis to research their upcoming book Mississippi: River of History.As they make their way to Memphis, Tennessee, National Geographic News will be posting photos and stories of the history they encounter on "Big Muddy."

On the Mississippi River in 1927, progress was everywhere. Thanks to bridges, trains, cars and trucks, people on foot could cross it without pause and without getting wheels or feet wet.

Nature had been or soon would be conquered, or so it seemed. Before the 19th century nothing man-made had ever moved faster than the speed of a horse. By 1927 it was commonplace. Man had taken control of