Martin Luther King Jr. Day is a United States holiday marking the birthdate of the Reverend Dr. Martin Luther King, Jr., observed on the third Monday of January each year, around the time of King's birthday, January 15. It is one of four United States federal holidays to commemorate an individual person.

Martin Luther King Jr. Day was founded as a holiday promoted by labor unions in contractnegotiations. After King's death in 1968, Rep. John Conyers introduced a bill in Congress to make King's birthday a national holiday, highlighting King's activism onbehalf of trade unionists. Unions did most of the promotion for the holiday throughout the 1970s. In 1976, trade unionists helped to elect Jimmy Carter, who endorsed the King Day bill. After that endorsement, union influence in the King holiday campaign declined, and the King Center turned to support from the corporate community and the general public. The success of this strategy was cemented when musician Stevie Wonder released the single "Happy Birthday" to popularize the campaign in 1980 and hosted the Rally for Peace Press Conference in 1981. Six million signatures were collected for a petition to Congress to pass the law, termed by a 2006 The Nation article as "...the largest petition in favor of an issue in United States History".

President Ronald Reagan opposed the holiday, relenting only after Congress passed the King Day Bill with an overwhelming veto-proof majority (338 to 90 in the House of Representatives and 78 to 22 in the Senate).

At the White House Rose Garden on November 2, 1983, Reagan signed a bill creating a federal holiday to honor King. It was observed for the first time on January 20, 1986.

[Source: http://en.wikipedia.org/wiki/Martin_Luther_King_Day]