John Charles Fremont's epic journey of discovery, along the route which would later become the Oregon Trail, is wonderfully portrayed by this detailed survey by Fremont's cartographer and travelling companion, Georg Carl Preuss. Their route is shown starting from the frontier settlement of Westport at the conjunction of the Kansas and Missouri Rivers. It then crosses the Rocky Mountains at South Pass to the Columbia River in Oregon, then south along the Sierra Nevada almost as far as the "Pueblo del los Angeles", Northeast to Lake Utah and finally east to the Arkansas River. This great map left only the interior of the Great Basin unexplored and, with its accompanying report, it had a profound influence on early emigrants to the Far West who followed in Fremonts footsteps along the Oregon Trail.