The Huntsville-Decatur Combined Statistical Area is the most populated sub-region of North Alabama, and is the second fastest growing region in the State of Alabama, with 510,088 living within the CSA. It is also currently the 65th largest CSA in the country.
The CSA is situated along the Tennessee River, and is made up of two separate metropolitan areas (Decatur and Huntsville) that are usually referred to as one. The Decatur MSA lies south of the Tennessee River, and the Huntsville MSA lies north.
Huntsville is the largest city in the area with a population of 168,132 people, and a metro population of 376,753. Decatur is the second largest city with a population of 55,758 people, and a metro population of 149,549. (All populations are based on the 2006 Estimated Population).
The geography of the Huntsville-Decatur Metro Area ranges from the tall peaks of the southern Appalachian Mountains, to the low valleys formed by the Tennessee River. Decatur sits on the southern shore of the Tennessee River, while Huntsville lies about 10 miles from the Tennessee River, and sits at the base of Monte Sano Mountain.
The heart of the Huntsville-Decatur Metro Area (Huntsville, Decatur, and Madison) is linked together by the 22 mile strip of Interstate 565.
Interstate 565 begins at the very edge of the Decatur City Limits at a major interchange with Interstate 65. At the interchange, Alternate US 72 and State Route 20 turn into a controlled access highway taking up the name Interstate 565 as it passes under Interstate 65 receiving traffic from the north - (Nashville), and south - (Birmingham / Decatur / Hartselle) on top of the nearly 40,000-51,000 vehicles per day driving from Decatur to Huntsville on the Alternate US 72 Corridor.
Plans are underway to extend Interstate 565 from the Interstate 65/Alternate US 72/State Route 20 interchange to the US 31/State Route 20/Alternate US 72 interchange in Decatur's Limestone County limits. Eventually the extended Interstate Highway will cross the Tennessee River's Wheeler Lake connecting with the proposed Memphis to Atlanta Highway.
As Interstate 565 exits the northern portion of the Wheeler National Wildlife Refuge, Madison Boulevard (formerly State Route 20) branches off of the interstate leading into Madison. After Madison Boulevard converges with Interstate 565 nine miles down the road, Research Park Boulevard, an important north/south expressway serving Cummings Research Park, Madison Square Mall, and Redstone Arsenal bypasses Huntsville's busier Memorial Parkway.
Interstate 565 winds past the US Space and Rocket Center. As it approaches downtown, the interstate becomes elevated. About a half mile after the elevated portion of the interstate begins is the largest interchange in Huntsville. Also known as "Malfunction Junction" to locals, the I-565/Memorial Parkway interchange carries over 150,000 vehicles a day. Memorial Parkway stretches from the Tennessee River to Normal. The Parkway feeds the congested 7-lane University Drive, also known as US 72. Also fed by the Parkway is the narrow, 5-lane Governors Drive (US 431) that serves southeast Huntsville, Hampton Cove, and Huntsville Hospital.
Eventually, Interstate 565 climbs up Chapman Mountain, and descends the other side towards Gurley as US 72.
Decatur, being only a midsized city, has not yet seen the conveniences of a drastically controlled access highway passing through the city limits.
Decatur's main roadways are 6th Avenue - (U.S. Route 31), and The Beltline - State Route 67.
6th Avenue, part of U.S. Route 31, begins as both State Route 20/Alternate US 72, and US 31 are carved out of the "Steamboat Bill" Hudson Memorial Bridge that crosses the Tennessee River at the north central part of town. AL 20/Alt US 72 continues west towards The Shoals, after The Beltline begins in the vicinity of the Solutia plant. After the Tennessee River bridges 6th Avenue continues southward where it eventually intersects with The Beltline. After that intersection, 6th Avenue continues southward now under the name of Decatur Highway towards Hartselle and Birmingham.
The Beltline was built as a western bypass to cure 6th Avenue of its congestion problem. The area around the Beltline experienced rapid growth, causing even worse traffic problems. The city's approach to this is to widen the road to six lanes, which should be completed by 2010.
The economy of the Huntsville-Decatur Area is made up mostly of Technical, Aerospace, Manufacturing, and Defensive jobs, and companies. More engineers per capita live in this metropolitan area than anywhere else in the United States. Huntsville is also home to the second largest research park in the country, Cummings Research Park.
The Huntsville-Decatur Metro Area is the second fastest growing region/metro area in the state of Alabama because of the ample job opportunities being instilled in the area. Both ports in the metro area are two of the busiest in the state. Huntsville International Airport is the second busiest in Alabama, and still growing, trailing Birmingham International Airport in Birmingham. The Port of Decatur, along the Tennessee River, has grown to be the largest/busiest along the Tennessee River.
The Tennessee Valley Authority (TVA) was established by President Franklin D. Roosevelt's New Deal plan, creating numerous dams, locks, nuclear power plants, coal power plants, along with many others, to create jobs along one of the most poverty ridden regions in the United States. The TVA has turned many tired North Alabama towns into some of the most technologically advanced cities in the country. A high quality of living, has helped to fuel the Huntsville and Decatur area's explosion into the aerospace, bio-technical, and other research market areas of the U.S..
The Tennessee Valley Authority has grown to be the largest public utility provider in the United States.