sentences:  The city rapidly grew into a large economic center within the Tennessee Valley and was a hub for travelers and cargo between Nashville and Mobile, as well as Chattanooga and New Orleans.Throughout the 20th century, the city experienced steady growth, but was eclipsed as the regional economic center by the fast-growing Huntsville during the space race.The city now finds its economy heavily based on manufacturing, mining, cargo transit, chemical, and high-tech companies such as Vulcan Materials, Daikin, Toray, and United Launch Alliance.