The roots of the colonization movement date back to various plans first proposed in the eighteenth century. From the start, colonization of free blacks in Africa was an issue on which both whites and blacks were divided. Some blacks supported emigration because they thought that black Americans would never receive justice in the United States. Others believed African-Americans should remain in the United States to fight against slavery and for full legal rights as American citizens. Some whites saw colonization as a way of ridding the nation of blacks, while others believed black Americans would be happier in Africa, where they could live free of racial discrimination. Still others believed black American colonists could play a central role in Christianizing and civilizing Africa.

The American Colonization Society was founded in the City of Washington in December 1816 for the purpose of colonizing the free people of color as an alternative to emancipation in the United States. A large portion of the citizens of the United States gave it their confidence and support. State, county and town societies, auxiliary to the parent society, were formed in nearly every State in the Union.

Many unexpected difficulties were encountered. Establishing a colony on so distant and unfrequented a shore, in the midst of a barborous people, without an armed force to protect it.

In 1818, Samuel J. Mills and Ebenezer Burgess were commissioned by the Society to proceed by the way of England to the English settlements and other ports of the western coasts of Africa, to acquire information and ascertain whether a suitable territory could be obtained for the establishment of a colony. They visited all the ports from Sierra Leone to Sherbro, a distance of about 120 miles. At this last place they found a small but prosperous colony of colored people settled by John Kizzel. John Kizzel had been brought from Africa when he was very young, and sold as a slave in South Carolina; during the revolutionary war he joined the British, and at its close was taken Nova Scotia, from where he sailed with a number of other colored persons to Africa. Mr. Burgess gave so satisfactory a report of his mission, that the society was encouraged to proceed in its enterprise.

By an Act of Congress on the 3rd of March, 1819, the President of the United States was authorized to restore to their own country, any Africans captured from American or foreign vessels, attempting to introduce them into the United States, in violation of law, and to provide by the establishment of a suitable agency on the African coast, for their reception, subsistence and comfort, until they could return to their relatives, or derive support from their own exertions. It was determined to make the station of the Government Agency, on the coast of Africa, the site of the colonial settlement; and to incorporate in the settlement, all the blacks delivered over by our ships of war, to the American Agent as the requisite preparations should be completed for their accommodations.

In February 1820 the Rev. Samuel Bacon went to Africa as principal agent of the United States. He embarked at New York in the ship Elizabeth, chartered by Government, and was accompanied by John P. Bankson, assistant, Dr. Samuel A. Crozer, agent of the American Colonization Society, and 88 emigrants, who, in consideration of their passage and other aid from government, agreed to prepare suitable accommodations for the reception of the Africans who might be delivered over to the protection of the agent. The expedition proceeded by way of Sierra Leone to the Island of Sherbro: the emigrants landed at Campelar, the place which had been chosen for the site of the proposed settlement. A short time before his death Mr. Bacon wrote in his journal, after describing his own labors and the sufferings of the people "Is it asked do I yet say colonize Africa? I reply, yes. The surpassing fertility of the African soil, the mildness of the climate during a great part of the year, the numerous commercial advantages, the stores of fish and herds of animals to be found here, invite her scattered children home. As regards myself, I counted the cost of engaging in this service, before I left America. I came to these shores to die , and any thing better than death, is better than I expect."

By 1821 several points on the coast had been visited, but no permanent arrangements had been made. The total failure of their first effort to establish a colony in Africa, only seemed to arouse the energies of the society to more vigorous and determined action.

In November another agent, Dr. Ayres, was instructed to visit Sierra Leone, and after ascertaining the condition of the surviving emigrants, to proceed down the coast in search of a suitable place for a settlement.

Capt. Stockton, with the United States schooner Alligator, was also ordered to the coast of Africa with instructions to assist Dr. Ayres in making proper arrangements for the emigrants. These gentlemen proceeded to Cape Montserado, about 250 miles from Sierra Leone to obtain, if possible, territory for the colony. After negotiating for several days with the chiefs of the country, they finally succeeded in obtaining a valuable tract of land including Cape Montserado.

After the purchase of the territory, Dr. Ayres employed two small schooners belonging to the colony and began removing the emigrants from Sierra Leone to their new settlement. The island on which the people had landed was entirely destitute of fresh water and fire wood, and shelter. An arrangement was made with King George, (who resided on the Cape, and claimed a sort of jurisdiction over the northern district of the peninsula of Montserado) to permit the settlers to pass across the river and clear away the heavy forest to make space for a town. By July of 1822 the emigrants were able to entirely abandon the island a take formal possession of Cape Montserado.

Selling life memberships was a standard fund-raising practice of benevolent societies such as the American Colonization Society. At thirty dollars each, the memberships were a popular gift for ministers. In 1825, one of the agents who sold the certificates in New England estimated that "not less than $50,000 have in this way been poured into the treasury of the Lord." This certificate bears a facsimile signature of Henry Clay, a founder of the ACS and its strong advocate in Congress. Clay succeeded former president James Madison as president of the society, serving from 1836 to 1849.

For many years the ACS tried to persuade the United States Congress to appropriate funds to send colonists to Liberia. Although Henry Clay led the campaign, it failed. The society did, however, succeed in its appeals to some state legislatures. In 1850, Virginia set aside $30,000 annually for five years to aid and support emigration. In its Thirty-Fourth Annual Report, the society acclaimed the news as "a great Moral demonstration of the propriety and necessity of state action!" During the 1850s, the society also received several thousand dollars from the New Jersey, Pennsylvania, Missouri, and Maryland legislatures.

Beginning in the 1830s, the society was harshly attacked by abolitionists, who tried to discredit colonization as a slave holder's scheme. William Lloyd Garrison's violent condemnations of colonization as a slaveholder's plot to perpetuate slavery created deep hostility between abolitionists and colonizationists. Intended to encourage emigration and answer anti-colonization propaganda, the ACS pamphlet answered questions about household items needed in Liberia, climate, education, health conditions, and other concerns about the new country. Citing abolitionist charges that colonizationists merely wanted "to get clear of the colored people of the United States from their political and social disadvantages . . . to place them in a country where they may enjoy the benefits of free government . . . and to spread civilization, sound morals, and true religion throughout Africa." After the Civil War, when many blacks wanted to go to Liberia, financial support for colonization had waned. During its later years the society focused on educational and missionary efforts in Liberia rather than emigration.

The Maryland State Colonization Society withdrew her support from the American Colonization Society and resolved to establish a colony in Liberia to send free people of color, of that State, that wished to emigrate. Soon after, the Young Men's Colonization Society of Pennsylvania, were induced to establish a separate colony.

The New York City Colonization Society united with the latter, under the active agency of Dr. Proudfit, the funds of the State were brought to their aid. Subsequently, the Mississippi State Colonization Society established a colony independent of the American Colonization Society. Thus, in 1838, there were four distinct colonies in Liberia, independent of, and unconnected with each other.

By the 1840s, Liberia had become a financial burden on the ACS. In addition, Liberia faced political threats, chiefly from Britain, because it was neither a sovereign power nor a bona fide colony of any sovereign nation. Because the United States refused to claim sovereignty over Liberia, in 1846 the ACS ordered the Liberians to proclaim their independence. In 1847, the colony became the independent nation of Liberia. By 1867, the society had sent more than 13,000 emigrants.