The 'Rust Belt' refers to the region of the northern Midwest of the United States, bordering the Great Lakes, that is home to many of the large industrial cities of America. In decades past it was on a par with the East Coast as the center of industry, commerce, population, and population density in the US, but recent decades have brought the decline of traditional heavy industries as well as a general pattern of out-migration to other regions of the country, particularly the South and West.
The easternmost extent of the Rust belt is Buffalo, in upstate New York on the shores of the Niagra River linking Lake Ontario with Lake Erie. The belt then sweeps through Northwestern Pennsylvania, including the steel centers of Erie and Pittsburgh. Across Northern Ohio are the factory towns of Cleveland, Akron, Youngstown, Toledo, and many others. The belt includes southern Michigan, especially Detroit, the motor city, and industrial towns such as Flint, Kalamazoo, and Benton Harbor. Continuing west, the decaying Indiana cities of Fort Wayne, Hammond, and Gary, on the shores of Lake Michigan lead the way to Chicago. The belt then continues north along the western shore of Lake Michigan, to include Milwaukee. It extends through Green Bay to the Duluth/Superior area of Minnesota and Wisconsin, on Lake Superior. Thus the Rust Belt includes parts of eight states, but the entirety of no states, and the southern shores of three of the five Great Lakes. If the adjoining and similar old industrial area of Southern Ontario, from west of Toronto through Niagra Falls is included, the Rust Belt is an international phenomenon.
The Rust Belt was the second part of North America to industrialize, after the factory towns of New England. The completion of the Erie Canal in Upstate New York linked the Great Lakes with the Hudson River and the Atlantic, allowing through shipping and beginning the industrialization of the region. Given its later starting date, the boundless resources of the vast frontier, and the shipping corridor provided by the Great Lakes system, the Rust Belt was the ideal locale for the expanding heavy industry that was transforming America in the late 19th century. The rapidly expanding factories drew immigrants from Eastern Europe, migrants from the farm land in their midst, and African Americans from the rural South to the towns and cities of the Rust Belt.
A pattern of production developed, all tied together by the Great Lakes and the massive freight railway system. Natural resources were extracted from the fringes - iron ore from Lake Superior and coal from central Pennsylvania - and loaded onto ships at ports like Duluth. The natural resources were then transformed into raw materials such as steel in cities like Pittsburgh and Cleveland, and then those raw materials were used to built finished products, such as cars, in other cities like Detroit.
Fortunes have changed in the years since World War 2. Factories have closed and relocated in other, non-unionized parts of America, and foreign countries like Mexico. Many people have left, looking to escape the dreary smoke stacks, long harsh winters, and feet upon feet of 'lake effect' snow that characterize the region. Many of the smaller towns of the Rust Belt were one industry or one company towns that have been devastated by the decline in heavy industry. Some of the most notorious are Gary, Indiana, Steubenville, Ohio, and Flint, Michigan. Some of the larger cities, most notably Chicago and Pittsburgh, had sufficient diversity in their economy that they were able to remake themselves to an extent. Most cities and towns in the Rust Belt have declined but not disappeared.