The most populous city in Michigan, Detroit is the county seat of Wayne County and the largest city on the U.S.-Canada border. It is a primary business, cultural, financial, and transportation center in the Metro Detroit area, a region of 5.2 million people, and serves as a major port on the Detroit River connecting the Great Lakes system to the Saint Lawrence Seaway. The Detroit area emerged as a significant metropolitan region within the United States as construction of a regional freeway system was completed in the 1950s and 1960s. With these commuting ties allowing social and economic integration across a larger area, the Detroit name sometimes refers to the three-county Urban Area (population 3,734,090, area of 1,337 square miles, as of the 2010 United States Census). Although the city has suffered a major population decline and economic downturn, Downtown Detroit has seen an increased role as an entertainment hub in the 21st century with the opening of three casinos, new stadiums, and a riverfront revitalization project.