slaves with them as the cotton plantations in Alabama expanded. The economy of the central Black Belt (named for its dark, productive soil) was built around large cotton plantations whose owners' wealth grew mainly from slave labor. The area also drew many poor, disenfranchised people who became subsistence farmers. Alabama had an estimated population of under 10,000 people in 1810, but it increased to more than 300,000 people by 1830. Most Native American tribes were completely removed from the state within a few years of the passage of the Indian Removal Act by Congress in 1830. From 1826 to 1846, Tuscaloosa served as Alabama's capital. On January 30, 1846, the Alabama legislature announced it had voted to move the capital city from Tuscaloosa to Montgomery. The first legislative session in the new capital met in December 1847. A new capitol building was erected under the direction of Stephen Decatur Button of Philadelphia. The first structure burned down in 1849, but was rebuilt on the same site in 1851. This second capitol building in Montgomery remains to the present day. It was designed by Barachias Holt of Exeter, Maine. Civil War and Reconstruction By 1860, the population had increased to 964,201 people, of which nearly half, 435,080, were enslaved African Americans, and 2,690 were free people of color. On January 11, 1861, Alabama declared its secession from the Union. After remaining an independent republic for a few days, it joined the Confederate States of America. The Confederacy's capital was initially at Montgomery. Alabama was heavily involved in the American Civil War. Although comparatively few battles were fought in the state, Alabama contributed about 120,000 soldiers to the war effort. A company of cavalry soldiers from Huntsville, Alabama, joined Nathan Bedford Forrest's battalion in Hopkinsville, Kentucky. The company wore new uniforms with yellow trim on the sleeves, collar and coattails. This led to them being greeted with "Yellowhammer", and the name later was applied to all Alabama troops in the Confederate Army. Alabama's slaves were freed by the 13th Amendment in 1865. Alabama was under military rule from the end of the war in May 1865 until its official restoration to the Union in 1868. From 1867 to 1874, with most white citizens barred temporarily from voting and freedmen enfranchised, many African Americans emerged as political leaders in the state. Alabama was represented in Congress during this period by three African-American congressmen: