The non-existent Buenaventura River, alternatively San Buenaventura River or Río Buenaventura, was once believed to run from the Rocky Mountains to the Pacific Ocean through the Great Basin region of what is now the western United States. The river was chronologically the last of several imagined incarnations of an imagined which would be for North America west of the Rockies what the Mississippi River was east of the Rockies. The hopes were to find a waterway from coast to coast, sparing the traveling around Cape Horn at the tip of South America.