Illinois is the fifth-most populous state of the United States of America, and is often noted for being a microcosm of the entire country. It is the most populous state in the Midwest region; however with 65% of its residents concentrated in the Chicago metropolitan area, most of the state has either a rural or a small town character. With Chicago in the northeast, small industrial cities and great agricultural productivity in central and northern Illinois, and natural resources like coal, timber, and petroleum in the south, Illinois has a broad economic base. Illinois is an important transportation hub; the Port of Chicago connects the Great Lakes to the Mississippi River via the Illinois River, and for decades, O'Hare International Airport has ranked as one of the world's busiest airports. As the "most average state",Illinois has long had a reputation as a bellwether both in social and cultural terms and politics.