Chattanooga is the fourth-largest city in the U.S. state of Tennessee, with a population of 167,674 as of the 2010 census. It is the seat of Hamilton County. Located in southeastern Tennessee on Chickamauga Lake and Nickajack Lake, which are both part of the Tennessee River, Chattanooga lies approximately 120 miles (190 km) to the northwest of Atlanta, Georgia, 120 miles (190 km) to the southwest of Knoxville, about 135 miles (217 km) to the southeast of Nashville, about 120 miles (190 km) to the northeast of Huntsville, Alabama, and about 148 miles (238 km) to the northeast of Birmingham, Alabama. Chattanooga abuts the Georgia border and is where three major interstate highways meet: I-24, I-75, and I-59.
The city, which has a downtown elevation of approximately 680 feet (210 m), lies at the transition between the ridge-and-valley portion of the Appalachian Mountains and the Cumberland Plateau. The city is therefore surrounded by various mountains and ridges. The official nickname for Chattanooga is the "Scenic City." Several unofficial nicknames include "River City", "Nooga", "Chat town", and "Gig City", demonstrating that Chattanooga currently has the fastest internet service in the Western Hemisphere.
Chattanooga is internationally known for the 1941 gold record song "Chattanooga Choo Choo", which was composed by Glenn Miller and his orchestra.
Since 1990, Chattanooga has been recognized as a Tree City USA community