Atlanta ( at-LAN-tÉ™) is the capital and most populous city in the U.S. state of Georgia. It is the seat of Fulton County, and a portion of the city extends into neighboring DeKalb County. With a population of 510,823 living within the city limits, Atlanta is the eighth most populous city in the Southeast and 38th most populous city in the United States according to the 2020 U.S. census. It is the principal city of the much larger Atlanta metropolitan area, the core of which includes Cobb, Clayton and Gwinnett counties, in addition to Fulton and DeKalb. Metro Atlanta is home to more than 6.3 million people (2023 estimate), making it the sixth-largest U.S. metropolitan area. Situated among the foothills of the Appalachian Mountains at an elevation of just over 1,000 feet (300 m) above sea level, Atlanta features unique topography that includes rolling hills, lush greenery, and the densest urban tree coverage of any major city in the United States. Atlanta was originally founded as the terminus of a major state-sponsored railroad, but it soon became the convergence point among several railroads, spurring its rapid growth. The largest was the Western and Atlantic Railroad, from which the name "Atlanta" is derived, signifying the city's growing reputation as a major hub of transportation. During the American Civil War, it served a strategically important role for the Confederacy until it was captured in 1864. The city was almost entirely burned to the ground during General William T. Sherman's March to the Sea. However, the city rebounded dramatically in the post-war period and quickly became a national industrial center and the unofficial capital of the "New South". After World War II, it also became a manufacturing and technology hub. During the 1950s and 1960s, it became a major organizing center of the American civil rights movement, with Martin Luther King Jr., Ralph Abernathy, and many other locals becoming prominent figures in the movement's leadership. In the modern era, Atlanta has remained a major center of transportation, with Hartsfield-Jackson International Airport becoming the world's busiest airport by passenger traffic in 1998 (a position it has held every year since, except for 2020), with an estimated 93.7 million passengers in 2022. With a nominal gross domestic product (GDP) of $473 billion in 2021, Atlanta has the 11th-largest economy among cities in the U.S. and the 22nd-largest in the world. Its economy is considered diverse, with dominant sectors in industries including transportation, aerospace, logistics, healthcare, news and media operations, film and television production, information technology, finance, and biomedical research and public policy. Atlanta established itself on the world stage when it won and hosted the 1996 Summer Olympics. The Games impacted Atlanta's development growth into the 21st century, and significantly sparked investment in the city's universities, parks, and tourism industry. The gentrification of some of its neighborhoods has intensified in the 21st century with the growth of the Atlanta Beltline. This has altered its demographics, politics, aesthetics, and culture.