In 1817 the Zebulon M. Pike reached St. Louis, the northern-most steamboat port on the Mississippi River. The western steamboat of later years was a credit to the frontier American mechanic who drew upon experience to build a large craft, eventually over 300 by 40 feet, which would carry heavy cargoes in shallow water against the strong Mississippi current. Owners boasted that steamboats could run on heavy dew, but seasonal variations in river depth limited their use, and medium sized steamboats needed at least four feet of water. The influence of the steamboat spread far and wide in the Mississippi Valley and hastened the development of the region. Snags, explosions, collisions, and fires sank many steamboats, and an 1867 investigation recorded 133 sunken hulks in the Mississippi between Cairo and St. Louis, a stretch rivermen called the 'Graveyard.' Even as north-south river trade flourished in the 1850's, transportation lines running east and west developed. Railroads, following a more direct route than winding rivers, began to haul freight to and from the Mississippi valley. Steamboats aided the North in the Civil War, but the reorientation of civilian commerce foreshadowed their decline. Although they continued to churn the Mississippi for the rest of the nineteenth century, they were eventually replaced by strings of barges guided by a single steamboat or later by a diesel boat that transported the cargoes individual steamboats had once carried.