Miami Beach is a coastal resort city in Miami-Dade County, Florida, United States. It is a principal city in the Miami metropolitan area of South Florida. The municipality is on natural and human-made barrier islands between the Atlantic Ocean and Biscayne Bay, the latter of which separates the Beach from the mainland city of Miami. The neighborhood of South Beach, comprising the southernmost 2.5 mi2 (6.5 km2) of Miami Beach, along with downtown Miami and the PortMiami, collectively form South Florida's commercial center. Miami Beach's population was 82,890 at the 2020 census. It has been one of America's preeminent beach resorts since the early 20th century.