In the Peoria area, there are six bridges that cross the Illinois River. Because of the topography of the cities, alignments of the numerous state routes that cross the Illinois River can be somewhat confusing. However, these routes are generally well marked. All bridges that span the Illinois River are required to be built a minimum of 70 feet (21 m) above the average river level, as the Illinois River is the main route for river traffic between New Orleans and Chicago. The Illinois River is part of a waterway system that begins in New Orleans, Louisiana and exits the Atlantic Ocean via Chicago and the Saint Lawrence Seaway.