Southeastern planters and traders from the Upper South brought 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.