Miami: Miami is a city located on the Atlantic coast in southeastern Florida and the county seat of Miami-Dade County, the most populous county in Florida and the eighth-most populous county in the United States with a population of 2,500,625. The 42nd largest city proper in the United States, with a population of 408,568, it is the principal, central, and most populous city of the South Florida metropolitan area, and the most populous metropolis in the Southeastern United States.