Decatur is also the core city of the two-county large Decatur Metropolitan Area which had 150,125 in 2006. Combined with the Huntsville Metropolitan Area, the two create the Huntsville-Decatur Combined Statistical Area, of which, Decatur is the second largest city.
Like many southern cities in the early 1800s, Decatur's early success was based upon its location along a river. Railroad routes and boating traffic pushed the city to the front of North Alabama's economic atmosphere. The city rapidly grew into a large economic center within the Tennessee Valley and was a hub for travelers and cargo between Nashville/Chattanooga and Mobile/New Orleans. Throughout the 20th century, the city experienced steady growth, but was eclipsed as the regional economic center by a fast growing Huntsville during the space race. The city now finds its economy heavily based on manufacturing industries, cargo transit, and hi-tech industries such as General Electric, and the United Launch Alliance.
As of the census of 2000, there were 53,929 people, 21,824 households, and 14,753 families residing in the city. The population density was 1,009.7 people per square mile (389.9/km²). There were 23,950 housing units at an average density of 448.4/sq mi (173.1/km²). The racial makeup of the city was 75.50% White, 19.56% Black or African American, 0.58% Native American, 0.70% Asian, 0.13% Pacific Islander, 2.22% from other races, and 1.33% from two or more races. 5.64% of the population were Hispanic or Latino of any race.
There were 21,824 households out of which 31.8% had children under the age of 18 living with them, 50.7% were married couples living together, 13.4% had a female householder with no husband present, and 32.4% were non-families. 28.9% of all households were made up of individuals and 10.7% had someone living alone who was 65 years of age or older. The average household size was 2.43 and the average family size was 2.99.
In the city the population was spread out with 25.4% under the age of 18, 8.8% from 18 to 24, 29.6% from 25 to 44, 23.1% from 45 to 64, and 13.1% who were 65 years of age or older. The median age was 36 years. For every 100 females there were 92.4 males. For every 100 females age 18 and over, there were 89.5 males.
The median income for a household in the city was $37,192, and the median income for a family was $47,574. Males had a median income of $37,108 versus $22,471 for females. The per capita income for the city was $20,431. About 11.9% of families and 14.9% of the population were below the poverty line, including 21.2% of those under age 18 and 11.1% of those age 65 or over.
Decatur is served by two major airports. The Huntsville International Airport, in suburban Huntsville is the second busiest airport in Alabama, behind Birmingham International Airport. The city is also served by the busiest regional airport in Alabama, the Pryor Field Regional Airport.
Decatur, being only a mid-sized city, has not yet seen the conveniences of a major controlled access highway passing through the city limits.
Decatur's main thoroughfares are 6th Avenue (US 31) and The Beltline (State Route 67). 6th Avenue begins as both Alabama 20, Alternate U.S. 72, and US 31 split after being carried by the twin-span "Steamboat Bill" Hudson Memorial Bridge that crosses Tennessee River at the north central part of town. Alabama 20/Alternate U.S. 72 continues west towards The Shoals, after the Beltline begins in the vicinity of the Solutia plant. 6th Avenue continues southward where it eventually intersects with Beltline Road. After that intersection, 6th Avenue continues southward to Birmingham as Decatur Highway.
The Beltline was built as a western bypass to relieve congestion on 6th Avenue. In doing so, however, this created another problem as sprawl quickly developed along the new arterial. Construction is currently under way to widen the road from four to six lanes with the project expected to be completed by 2010.
Plans are also under way to construct a controlled access beltway from Interstate 65 south of the city to Alternate U.S. 72 in Lawrence County, known as Veteran's Parkway.
In addition, there are plans to transform Alabama Highway 20/Alternate US 72 into an extension of Interstate 565 into the city. Governor Bob Riley has said he will make sure that plans for the road will be put on the fast track, since more than 85 vehicle accidents occur on Highway 20's final approach into Decatur each year.