Chattanooga is a city in the U.S. state of Tennessee, with a population of 177,571 in 2016. The fourth-largest Tennessee city, it is the seat of Hamilton County. Located in southeastern Tennessee in East Tennessee, on the Tennessee River, served by multiple railroads and Interstate highways, Chattanooga is a transit hub. Chattanooga lies 120 miles northwest of Atlanta, Georgia, 120 miles southwest of Knoxville, Tennessee, 135 miles southeast of Nashville, Tennessee, 120 miles northeast of Huntsville, Alabama, and 148 miles northeast of Birmingham, Alabama.The city, with a downtown elevation of approximately 680 feet, lies at the transition between the ridge-and-valley portion of the Appalachian Mountains and the Cumberland Plateau. Surrounded by mountains and ridges, the official nickname for Chattanooga is the Scenic City, reinforced by the city's reputation for outdoor activities.