St. Louis is an independent city and the second-largest city in the U.S. state of Missouri. St. Louis was found in 1763 by French explorers Pierre Laclède de Liguest and Auguste Chouteau. Rapids on the Mississippi River made St. Louis the northernmost navigable port for many large boats, and by the 1850s, St. Louis had become the largest US city west of Pittsburgh, and the second-largest port in the country, with a commercial tonnage exceeded only by New York City. St. Louis is sited near the confluence of the Missouri and the Mississippi Rivers, is the heart of Greater St. Louis, a metropolitan area of nearly three million people in Missouri and Illinois, the Illinois portion of which is commonly referred to as the Metro-East.