the economic backbone of early america, running north to south for more than 2000 miles, carrying the people and cargo that helped to turn this country from a fledgling upstart into a powerhouse. for much of the 19th century, steamboats like this ruled the river. but in 1879, construction began on a transcontinental train line, that would link the newfound prosperity with the isolated far west. connecting the gulf of mexico with the pacific ocean. on this journey i'll be following the railroad that pushed the american dream along the mexican border all the way to california. every trip is unique. it's a moving city. and i will be meeting some of the people who help define