Miami-Dade County is a county located in the southeastern part of the U.S. state of Florida. The county had a population of 2,701,767 as of the 2020 census, making it the most populous county in Florida and the seventh-most populous county in the United States. It is Florida's third largest county in terms of land area with 1,946 square miles. The cou…Miami-Dade County is a county located in the southeastern part of the U.S. state of Florida. The county had a population of 2,701,767 as of the 2020 census, making it the most populous county in Florida and the seventh-most populous county in the United States. It is Florida's third largest county in terms of land area with 1,946 square miles. The county seat is Miami, the core of the nation's ninth-largest and world's 65th-largest metropolitan area with a 2020 population of 6.138 million people, exceeding the population of 31 of the nation's 50 states as of 2022.