The Rust Belt occupies the Midwestern and Northeastern US. Cities in this area include New York, Chicago, Philadelphia, Detroit, Washington, and Boston.

Way too many to list here.

yup

the migration of americans from the rust belt to the sunbelt

The Manufacturing Belt was called the Rust Belt in the latter decades of the 20th century because the word that describes the deterioration of iron into rust was an appropriate name to give to a region where the iron and steel and related industries were in great decline. The South, West, and Southwest were called the Sun Belt because of their sunny climates; Rust Belt mimicked that name. In many cases, old factories had literally turned to rust, but the whole region was considered obsolete and deteriorated.