The United States. city of Atlanta, which is the capital of the southeastern state of Georgia, is situated on the Eastern Continental Divide, which runs through the downtown section of the metropolitan area. The 132.4-square-mile city also sits atop of a ridge among the Appalachian Mountain foothills, located south of the Chattahoochee River. Atlanta's elevation of 1,050 feet above sea level makes it the highest of the major American cities located east of the Mississippi River.
Most of Atlanta is encircled by Interstate 285, which is known locally as "the Perimeter." The outer suburbs and exurbs are referred to as OTP, an acronym for "Outside the Perimeter." The city is the county seat of Fulton County, in the northwestern section of the state. A small area of Atlanta extends into DeKalb County to the east.
Atlanta ranks ninth in U.S population size, with more than 5.5 million city residents. It is also a major transportation hub with its airport, Hartsfield-Jackson Atlanta International Airport, ranked as the busiest airport worldwide since 1998. The city is marked by dense tree coverage and contains rolling hills. Because of an abundance of trees rarely found in a major city, Atlanta has gained the reputation of a "city in a forest." The city's tree coverage is at 36 percent, significantly above the national average of 27 percent.