The idea that
slaves of
African descent in the
Americas could be freed and then taken back to
Africa, somewhat popular in the pre-
Civil War U.S. and other locations which had slaves around that time. The country of
Liberia was founded by the
U.S. as a home for these freed slaves (and
Sierra Leone was to serve a similar purpose for former slaves from areas that were still
British colonies).
In colonial days in the 13 colonies, nearly everyone believed that slavery would not last forever -- until the 1830s, most Southerners tended to apologize for the existence of slavery in their area rather than defending it. However, they were still anti-Negro enough not to want to have huge numbers of former slaves living in the South (later several states would pass laws making it extremely difficult to for owners to free slaves if they wanted to).
The idea of recolonizing the freedmen seemed like the logical thing to do at this time, but it would cost a huge amount. In 1817 the American Colonization Society was founded to try and provide transport to Africa, but it was unable to get Federal support or to raise anywhere near the amount of money that would be needed; between 1821 and 1860, they sent only around 15,000 people to Africa, a fraction of the number of slaves born in the same period.
The other problem with recolonization is that no one wanted to go. The slave trade directly from Africa had been abolished in the U.S., so the vast majority of slaves and freedmen had been born in the Americas and had no interest in going to a strange land to live. Those who did go often died of tropical diseases, or survived but wrote letters to American friends saying "tell Uncle Pleasant that we have snakes here 15 to 20 feet and can swallow a man, deer, or hog with ease."
For these reasons, the idea of recolonization gradually ceased to play a part in the discussions of abolitionists and the arguments on the subject of slavery went in different directions until the Civil War.
Quotation from A History of the Old South by Clement Eaton