Archer Alexander was born around 1810, (exact date unknown) near Richmond, Virginia. Archer was a slave and in 1863 during the Civil War he fled to St. Louis, then under martial law. He was formally liberated the same year. Archer served as the model for "the freedman" in the bronze group by Thomas Ball, standing in the capitol grounds in Washington, and known as "Freedom's Memorial."   

(Freedom's Memorial Statue is depicted on the 13th Amendment stamp issued in 1940.) 

In 1831 Archer's master took him to Missouri. During the reign of terror in that state at the outbreak of the war he learned that the pro-slavery party had cut the timbers of a certain bridge so that it should break down under a train carrying a detachment of national troops about to pass over it.

At the risk of his life he conveyed the information to a well-known union man, and the detachment was saved. Alexander was suspected as the informant and arrested by a pro-slavery committee. He escaped to the North and secured employment in St. Louis under a provost marshal's certificate. Until the emancipation proclamation assured his permanent freedom he was in constant danger from kidnappers. Although almost wholly illiterate, he had a shrewd intelligence and was a skilled and efficient workman. A stone commemorating his capture as a fugitive slave has been raised on the spot where he was taken when making his escape from slavery.

Archer Alexander died on December 8, 1879 in St. Louis, Missouri.

The Thirteenth Amendment to the U.S. Constitution:

After the Civil War ended three additional amendments were added to the Bill of Rights to help ensure freedom and full rights for the former slaves.

President Lincoln issued his Emancipation Proclamation in 1863. This document declared that slaves in all states in rebellion against the Union were to be freed, but did not actually effect the freedom of any slaves. The 13th Amendment abolished slavery in all states of the Union.

The 13th Amendment abolished slavery.

Section 1. Neither slavery nor involuntary servitude, except as a punishment for crime whereof the party shall have been duly convicted, shall exist within the United States, or any place subject to their jurisdiction.

Section 2. Congress shall have power to enforce this article by appropriate legislation.

The 14th Amendment granted citizenship to former slaves.

In 1954 the Supreme Court applied the equal protection clause of the Fourteenth Amendment in its landmark decision of Brown v. Board of Education of Topeka, which  ruled that racial segregation in public schools was unconstitutional. In the 1960s and '70s the equal protection clause was used by the Supreme Court to extend protections to other areas, including zoning laws, voting rights, and gender discrimination.

Section 1. All persons born or naturalized in the United States, and subject to the jurisdiction thereof, are citizens of the United States and of the state wherein they reside. No state shall make or enforce any law which shall abridge the privileges or immunities of citizens of the United States; nor shall any state deprive any person of life, liberty, or property, without due process of law; nor deny to any person within its jurisdiction the equal protection of the laws.

Section 2. Representatives shall be apportioned among the several states according to their respective numbers, counting the whole number of persons in each state, excluding Indians not taxed. But when the right to vote at any election for the choice of electors for President and Vice President of the United States, Representatives in Congress, the executive and judicial officers of a state, or the members of the legislature thereof, is denied to any of the male inhabitants of such state, being twenty-one years of age, and citizens of the United States, or in any way abridged, except for participation in rebellion, or other crime, the basis of representation therein shall be reduced in the proportion which the number of such male citizens shall bear to the whole number of male citizens twenty-one years of age in such state.

Section 3. No person shall be a Senator or Representative in Congress, or elector of President and Vice President, or hold any office, civil or military, under the United States, or under any state, who, having previously taken an oath, as a member of Congress, or as an officer of the United States, or as a member of any state legislature, or as an executive or judicial officer of any state, to support the Constitution of the United States, shall have engaged in insurrection or rebellion against the same, or given aid or comfort to the enemies thereof. But Congress may by a vote of two-thirds of each House, remove such disability.

Section 4. The validity of the public debt of the United States, authorized by law, including debts incurred for payment of pensions and bounties for services in suppressing insurrection or rebellion, shall not be questioned. But neither the United States nor any state shall assume or pay any debt or obligation incurred in aid of insurrection or rebellion against the United States, or any claim for the loss or emancipation of any slave; but all such debts, obligations and claims shall be held illegal and void.

Section 5. The Congress shall have power to enforce, by appropriate legislation, the provisions of this article.

The 15th Amendment guaranteed former male slaves the right to vote.

Section 1. The right of citizens of the United States to vote shall not be denied or abridged by the United States or by any state on account of race, color, or previous condition of servitude.

Section 2. The Congress shall have power to enforce this article by appropriate legislation.

Sources: 
Encyclopedia Britannica  
Encyclopedia Africana   
National Archives and Records Administration