In the early 1800s a major social movement, the American Colonization Society, secured marked support in the United States. First popular in the 1820s and early 1830s, the movement waned in the late 1830s and 40s. It was not until the 1850s, when slavery increasingly polarized the nation, that the movement regained strength. Despite the endorsement of prominent humanitarians and sympathetic politicians in both the North and South, the colonization movement faltered in its initial goal of colonizing free blacks and its later efforts to encourage voluntary and gradual emancipation. This work explores the Society's organization, purpose, growth, and the various factors that led to its ultimate failure in addressing the existence of slavery in a society still experimenting with democracy.