The phrase "rust belt" refers to a region in the United States that used to have a strong manufacturing industry but experienced a decline. It is named after the rust that forms on abandoned factories and plants. Full definition
Most important is coming from — not a quaint small town right out of It's a Wonderful Life — but a gritty rust belt city in sharp decline. (nystateofpolitics.com)
We have wondered if the attraction of cheap real estate might lead to the revitalization of rust belt cities into greener, more self sufficient communities. (treehugger.com)