Martin Luther King Day is a federal holiday held on the  third Monday of January. It celebrates the life and achievements of  Martin Luther King Jr., an influential American civil rights leader. He  is most well-known for his campaigns to end racial segregation on public  transport and for racial equality in the United States.  

Martin  Luther King Day is one of the United States' most celebrated holidays.  It honors the life of a man who promoted equal rights. This illustration  is based on artwork from ©iStockphoto.com/Soren Pilman
What do people do?
Martin Luther King Day is a relatively new federal holiday and there  are few long standing traditions. It is seen as a day to promote equal  rights for all Americans, regardless of their background. Some  educational establishments mark the day by teaching their pupils or  students about the work of Martin Luther King and the struggle against  racial segregation and racism. In recent years, federal legislation has  encouraged Americans to give some of their time on this day as  volunteers in citizen action groups.
Martin  Luther King Day, also known as Martin Luther King’s birthday  and Martin Luther  King Jr Day, is combined with other days in different  states. For example, it  is combined with Civil Rights Day in Arizona and New Hampshire, while it is observed together with Human  Rights Day in Idaho. It is also a day that is combined with Robert E.  Lee’s birthday in some states. 
Public life
Martin Luther King Day is a federal holiday, but has slightly different  names in some states. Non-essential Government departments are closed,  as are many corporations. Some schools and colleges close but others  stay open and teach their students about the life and work of Martin  Luther King.   Small companies, such as grocery stores and restaurants tend to be open,  although a growing number are choosing to close on this day. Some  compensate by opening on Washington's Birthday instead. Recent federal  legislation encourages Americans to give some of their time on Martin  Luther King Day as volunteers in citizen action groups. Public transit  systems may or may not operate on their regular schedule.   
Background
Martin Luther King was an important civil rights activist. He was a  leader in the movement to end racial segregation in the United States.  His most famous address was the "I Have A Dream" speech. He was an  advocate of non-violent protest and became the youngest man to be  awarded the Nobel Peace Prize. He was assassinated in 1968.   In 1968, shortly after Martin Luther King died, a campaign was started  for his birthday to become a holiday to honor him. After the first bill  was introduced, trade unions lead the campaign for the federal holiday.  It was endorsed in 1976. Following support from the musician Stevie  Wonder with his single "Happy Birthday" and a petition with six million  signatures, the bill became law in 1983. Martin Luther King Day was  first observed in 1986, although it was not observed in all states until  the year 2000.