The taking of Alta California during the Mexican-American War and the California gold rush suddenly made the west coast of North America a priority for the U.S. government. To exploit the commercial opportunities of the new territory, shippers needed aids to navigation, starting with charts. Congress appropriated money to repair "Jefferson" so she could begin to survey the west coast. In 1850 she sailed from Baltimore to Philadelphia. She was hauled out on the Southwark marine railway where a new boiler was installed and she was converted to sidewheel propulsion.