Martin Luther King, Jr. Day is on the 20th of January in 2014. It is always observed on the 3rd Monday of January in the United States. It celebrates the life of the activist who protested against racial discrimination during the civil rights movement.
As of 2000, it is observed in all fifty U.S. states. In some states, the day is known by alternative names, like "Human Rights Day," "Civil Rights Day" and "Lee-Jackson-King Day."
Martin Luther King, Jr. Day is a legal federal holiday, and as a result, non-essential governmental offices are closed and all federal employees are paid for the holiday.
It is also a state holiday, with South Carolina being the final state to recognize Martin Luther King, Jr. Day as a paid holiday for all state employees.
Private sector employers are not required to pay employees extra (over and above your normal rate of pay) for working on a holiday unless you have a contract that stipulates holiday pay. Employers may designate holidays as paid time off, however they aren't required to give you the holiday off from work.