The Three-Fifths Compromise was a compromise between Southern and Northern states reached during the Philadelphia Convention of 1787 in which three-fifths of the enumerated population of slaves would be counted for representation purposes regarding both the distribution of taxes and the apportionment of the members of the United States House of Representatives. It was proposed by delegates James Wilson and Roger Sherman.
Delegates opposed to slavery generally wished to count only the free inhabitants of each state, but delegates supportive of slavery, on the other hand, generally wanted to count slaves in their actual numbers. Since slaves could not vote, slaveholders would thus have the benefit of increased representation in the House and the Electoral College. The final compromise of counting "all other persons" as only three-fifths of their actual numbers reduced the power of the slave states relative to the original proposals, but increased it over the northern position.
The Three-Fifths Compromise is found in Article 1, Section 2, Paragraph 3 of the United States Constitution:
Representatives and direct Taxes shall be apportioned among the several States which may be included within this Union, according to their respective Numbers, which shall be determined by adding to the whole Number of free Persons, including those bound to Service for a Term of Years, and excluding Indians not taxed, three fifths of all other Persons.
The three-fifths ratio originated with a 1783 amendment proposed to the Articles of Confederation. The amendment was to have changed the basis for determining the wealth of each state, and hence its tax obligations, from real estate to population, as a measure of ability to produce wealth. The proposal by a committee of the Congress had suggested that taxes "shall be supplied by the several colonies in proportion to the number of inhabitants of every age, sex, and quality, except Indians not paying taxes." The South immediately objected to this formula since it would include slaves, who were viewed primarily as property, in calculating the amount of taxes to be paid. As Thomas Jefferson wrote in his notes on the debates, the southern states would be taxed "according to their numbers and their wealth conjunctly, while the northern would be taxed on numbers only."
After proposed compromises of 1⁄2 by Benjamin Harrison of Virginia and 3⁄4 by several New Englanders failed to gain sufficient support, Congress finally settled on the 3⁄5 ratio proposed by James Madison. But this amendment ultimately failed, falling two states short of the unanimous approval required for amending the Articles of Confederation (only New Hampshire and New York were opposed).
The proposed ratio was, however, a ready solution to the impasse that arose during the Constitutional Convention. In that situation, the alignment of the contending forces was the reverse of what had obtained under the Articles of Confederation. In amending the Articles, the North wanted slaves to count for more than the South did because the objective was to determine taxes paid by the states to the federal government. In the Constitutional Convention, the more important issue was representation in Congress, so the South wanted slaves to count for more than the North did.
"Much has been said of the impropriety of representing men who have no will of their own. ...They are men, though degraded to the condition of slavery. They are persons known to the municipal laws of the states which they inhabit, as well as to the laws of nature. But representation and taxation go together. ...Would it be just to impose a singular burden, without conferring some adequate advantage?" - Alexander Hamilton 
The three-fifths ratio, or "Federal ratio", had a major effect on pre-Civil War political affairs due to the disproportionate representation of slaveholding states relative to voters. For example, in 1793 southern slave states would have been apportioned 33 seats in the House of Representatives had the seats been assigned based on the free population; instead they were apportioned 47. In 1812, slaveholding states had 76 instead of the 59 they would have had; in 1833, 98 instead of 73. As a result, southerners dominated the Presidency, the Speakership of the House, and the Supreme Court in the period prior to the Civil War.
Historian Garry Wills has postulated that without the additional slave state votes, Jefferson would have lost the presidential election of 1800. Also, "...slavery would have been excluded from Missouri...Jackson's Indian removal policy would have failed...the Wilmot Proviso would have banned slavery in territories won from Mexico....the Kansas-Nebraska bill would have failed...." However, other historians have criticized Wills' analysis as simplistic. For example, while the Three-Fifths Compromise could be seen to favor Southern states (which generally had larger slave populations), the Connecticut compromise tended to favor the Northern states (which were generally smaller). Support for the new Constitution rested on the balance of these sectional interests.
Following the Civil War and the abolition of slavery by the Thirteenth Amendment to the United States Constitution (1865), the three-fifths clause was rendered moot. Section 2 of the Fourteenth Amendment to the United States Constitution (1868) later superseded Article 1, Section 2, Clause 3. It specifically states that "Representatives shall be apportioned ...counting the whole number of persons in each State, excluding Indians not taxed..."
- Paul Finkelman, “How The Proslavery Constitution Led To The Civil War” Rutgers Law Journal Volume 43 Fall/Winter 2013 Number 3, p405
- Wills pg. 51
- Hannis Taylor (1911). The Origin and Growth of the American Constitution: An Historical Treatise. Houghton Mifflin Company. p. 131.
- Wills pg. 51-52
- Wills pg 53.
- Hamilton pg. 237
- Jonathan Elliot, ed. (1866). The Debates In The Several State Conventions On The Adoption Of The Federal Constitution, As Recommended By The General Convention At Philadelphia, In 1787. J.B. Lippincott & Co. Washington: Taylor & Maury. p. 237.
- Wills pg. 5-6.
- "A SLAVE TO THE SYSTEM? Thomas Jefferson and Slavery". Hoover Institution. January 19, 2004. Retrieved 2008-02-20.
- Banning, Lance (August 31, 2004). "Three-Fifths Historian". The Claremont Institute. Retrieved 2008-01-21.
- Wills, Garry (2003). "Negro President": Jefferson and the Slave Power. Boston: Houghton Mifflin. ISBN 0-618-34398-9.
- Walton, Hanes, Jr.; Smith, Robert C. (2006). American Politics and the African American Quest for Universal Freedom (3rd Edition ed.). New York: Pearson Longman. ISBN 0-321-29237-5.
- Wiencek, Henry (2004). An Imperfect God: George Washington, His Slaves, and the Creation of America. New York: Farrar, Straus, and Giroux. ISBN 0-374-52951-5.
- Report of the Brown University Steering Committee on Slavery and Justice