The 23rd Amendment grants presidential voting rights to citizens of the District of Columbia and representation for D.C. in the Electoral College.
When the District of Columbia was created as the seat of the government of the new United States, it was envisioned as not a permanent residence so much as a temporary residence, for those serving in Government. Article I, Section 8 mentions the District but only in reference to its role in housing the Government. The District grew in population through the years, however, and soon housed many people who didn't fit the original description.
As early as 1890, a member of Congress introduced legislation calling for D.C. voting rights. The measure had little support, however. One main proponent was Theodore Noyes, a writer for the Washington Evening Star. In addition to advocating on behalf of D.C. residents, Noyes helped found the Citizens' Joint Committee on National Representation for the District of Columbia, which continued its efforts after Noyes died in 1946.
Congress agreed on the wording of the Amendment on June 17, 1960, and sent it to the states. Hawaii, the last state to join the Union, was the first to ratify, just six days later. The necessary 38th state, Kansas, ratified on March 29, 1961. It was too late for the election of 1960, so the first presidential election in which D.C. voters could vote for President and Vice-president was in 1964.
The Text of the 23rd Amendment
Section 1. The District constituting the seat of Government of the United States shall appoint in such manner as the Congress may direct:
A number of electors of President and Vice President equal to the whole number of Senators and Representatives in Congress to which the District would be entitled if it were a State, but in no event more than the least populous State; they shall be in addition to those appointed by the States, but they shall be considered, for the purposes of the election of President and Vice President, to be electors appointed by a State; and they shall meet in the District and perform such duties as provided by the twelfth article of amendment.
Section 2. The Congress shall have power to enforce this article by appropriate legislation.