Their first priority was to explore the American West to make it accessible. Early on they worked to make the Mississippi and Ohio Rivers navigable. The work of charting these rivers actually started under the Topographical Bureau over a decade before the establishment of the Corps of Topographical Engineers. During the mid-1800s, they worked on floodind issues of major rivers. They designed lighthouses, mapped navigational routes and worked on many other federal projects. The General Survey Act gave them the authority to survey all canals and roads in the United States. They surveyed the National Road that connected the Potomac and Ohio Rivers. This was a main transport path to the West for thousands of settlers.