The map shows sea travel from coast to coast in the 1800s. A map titled Sea Travel from Coast to Coast, 1800's. It shows that, to travel from the East Coast of the United notes to the West Coast by sea, one would have to travel all the way down the eastern coast of South America to the southern tip of South America, then up the western coast of South America and Mexico before reaching the West Coast of the United notes. Based on the map, which best explains why the United States wanted to build a canal across Central America? The US intended to annex additional foreign territories in the area. The US wanted a more-efficient way to move troops into Central America. The US sought a direct route to get supplies to South America's mainland. The US needed an easier and faster way to get goods from coast to coast.