The Census Bureau–defined region has a total area of with of that being land mass. Although it lacks a unified cultural identity, the Northeastern region is the nation's most economically developed, densely populated, and culturally diverse region. Of the nation's four census regions, the Northeast has the second-largest percentage of residents living in an urban setting, with 85 percent, and is home to the nation's largest metropolitan area. The Northeast is home to most of the Northeast megalopolis, the most economically significant and second most-populated of eleven mega regions within the United States, accounting for 20% of US GDP.