Out of all the leaders of the civil rights movement why is Martin Luther King the only one with a national holiday?

It appears from the history of the attempts to introduce his birthday as a national holiday that it is extraordinary that we have any African-American at all honored this way.  The first attempts began shortly after King's assassination in 1968, but Congress did not pass a bill for this holiday until 1983, to be effective in 1986.  The argument stated was that the cost would be a burden to the taxpayers, since national holidays were paid days off for federal employees.  One has to wonder, though, whether this argument would have been made for someone who was not African-American. 

There were no doubt many other important civil rights figures. Rosa Parks would have made a good pick, since we have no women honored this way.  But I do think the two factors that led to King as the choice were his outsize contributions to the movement and his martyrdom.  Most people, if asked to name leaders of the civil rights movement are likely to have a difficult time thinking beyond King.  And his horrific assassination was his ultimate sacrifice to the movement, a sacrifice he certainly knew was possible and perhaps even likely. 

It is clear from just following the daily news that we are not in a post-racial world yet, any more than we are in a post-sexist one.  So, I think we have to count ourselves lucky to have one African-American honored with a national holiday, and King, with all that he did accomplish and his sacrifice of his life, seems to me to be a very good choice.