Can anyone explain Mississippi's weird results from 1956-1964?

[Starbucks Union Thug HokeyPuck]

1956:
Stevenson: 58
Eisenhower: 24
Unpledged?: 17

1960:
Unpledged?: 39
Kennedy: 34
Nixon: 25

1964:
Goldwater: 87!?
Johnson: 12

So... how exactly did MS run it's elections for there to be unpledged electors on the ballot, and why did the voters vote for something that would make no difference?  (protest vote?).  And how the hell did Goldwater manage 87% in the state when Johnson won in the biggest landslide in modern history?  I know the Deep South was Goldwater's base and all... but other Southern whites seemed OK enough with Johnson (a Southerner) that Goldwater wasn't racking up such ridiculous numbers. 

It just seems like the rest of the country was "normal" in a way... and for every election over 12 years Mississippi went off on a tangent all by itself. 

[Starbucks Union Thug HokeyPuck]

Thanks for the answers... I knew racism had something to do with it, but had no idea about the actual MS election process.  

Still find it fascinating that in 1964 MS voters (who I'm assuming were all white), were SO homogenous.  

EDIT: then again, checking the 2008 exit poll, whites in MS went 88-11 McCain.  LA and AL are similar, and outside of those 3 it seems to normalize to a degree.  This is 2008 for god's sake, that's just unbelievable.