Springfield is the third largest city in the U.S. state of Missouri. It is the county seat of Greene County. On July 1, 2008, the estimated population was 156,206. The Springfield Metropolitan Area, population 426,144, and includes the counties of Christian, Dallas, Greene, Polk and Webster. The estimated population inside a 50-mile (80 km) radius of Springfield was 662,587 as of 2009. Springfield is near the population center of the United States, about 80 miles (130 km) to the east. Springfield's nickname is The Queen City of the Ozarks. It is also known as The Cultural Center of the Ozarks, The Gateway to the Ozarks, and The Birthplace of Route 66.