The city (downtown elevation approximately 685 feet), which lies at the transition between the ridge-and-valley portion of the Appalachian Mountains and the Cumberland Plateau, is surrounded by mountains and ridges. Chattanooga's official nickname is the "Scenic City".
As of the census of 2000, there were 155,554 people, 65,499 households, and 39,626 families residing in the city. The population density was 1,150.5 people per square mile (444.2/km²). There were 72,108 housing units at an average density of 533.3/sq mi (205.9/km²). The racial makeup of the city was 59.71% White, 36.06% Black, or African American, 0.29% Native American, 1.54% Asian, 0.11% Pacific Islander, 1.01% from other races, and 1.30% from two or more races. 2.11% of the population were Hispanic or Latino of any race. The 2006 revised estimated population was 168,293 which is an 8.4% percent increase over the original 2006 estimate.
There were 65,499 households out of which 25.3% had children under the age of 18 living with them, 39.2% were married couples living together, 17.3% had a female householder with no husband present, and 39.5% were non-families. 33.5% of all households were made up of individuals and 11.6% had someone living alone who was 65 years of age or older. The average household size was 2.29 and the average family size was 2.92.
In the city the population was spread out with 22.4% under the age of 18, 10.8% from 18 to 24, 28.8% from 25 to 44, 22.8% from 45 to 64, and 15.2% who were 65 years of age or older. The median age was 37 years. For every 100 females there were 89.3 males. For every 100 females age 18 and over, there were 85.2 males.
The median income for a household in the city was $32,006, and the median income for a family was $41,318. Males had a median income of $31,375 versus $23,267 for females. The per capita income for the city was $19,689. About 14.0% of families and 17.9% of the population were below the poverty line, including 27.0% of those under age 18 and 13.8% of those age 65 or over.
Chattanooga's Metropolitan Statistical Area, which includes Hamilton, Marion, and Sequatchie counties in Tennessee and Catoosa, Dade, and Walker counties in Georgia, had an estimated population of 496,704 in 2006. The Chattanooga-Cleveland-Athens Combined Statistical Area which also includes Bradley, Polk, and McMinn Counties in Tennessee had an estimated population of 658,201 in 2006.
Considered to be a gateway to the Deep South, Chattanooga's transportation infrastructure has developed into a complex and intricate system of railroads, streets, airports and waterways.
See also List of Tennessee state highways
The city is served by a publicly run bus company, the Chattanooga Area Regional Transportation Authority. CARTA operates 17 routes, including a free electric shuttle service in the downtown area and free wireless internet on certain "smartbuses"..
Despite a new emphasis on the technology and service sectors, Chattanooga maintains ties to the past and still serves as a major freight hub with Norfolk Southern (NS) and CSX running trains on their own (and each other's) lines. The Norfolk Southern Railway's enormous DeButts Yard is just east of downtown, Shipp's Yard and CSX's Wauhatchie Yard are southwest of the city. Indeed, the two railroad companies are among the largest individual landowners in the city (the Federal Government is another). The Tennessee Valley Railroad Museum, the largest historic operating railroad in the South, and the Chattooga and Chickamauga Railway also provides railroad service in Chattanooga.
Since both NS and CSX both run through Chattanooga, here are the lines that run through the town (the AAR codes are used for the following railroads: NS for Norfolk Southern, CSXT for CSX Transportation, TNVR for Tennessee Valley Railroad Museum, and CCKY for Chattooga and Chickamauga Railway):
Also, the Incline Railway, as well as being a tourist attraction, is sometimes used for commuting by Lookout Mountain residents, particularly during wintry weather, when travelling up and down the mountain could be very dangerous.
Despite the relatively high level of freight rail activity, there is no passenger rail service in the city for either commuters or long-distance travelers.
Being bisected by a major waterway, Chattanooga has several large bridges over the Tennessee River. They are, from west to east:
The Chattanooga Metropolitan Airport offers non-stop service to various domestic destinations via regional and national airlines, including Delta Connection, American Airlines, US Airways, Northwest Airlines and Allegiant.