Mississippi took the first step to prohibit african americans from voting when it required that all citizens registering to vote pay what tax
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Mississippi took the first step to prohibit African Americans from voting with the "poll tax." 
 A poll tax levied on every adult, without reference to income or resources.

Hello there!
Its a great pleasure for me to be helping you today!
So here, Mississippi took the first step to prohibit African Americans from voting when it required that all citizens registering to vote pay the poll tax. 
Hope i helped today!
~Sammy)

C. it's a true fact. i know because we are studying about the great depression. so it best illustrates a claim of fact. thx. have a wonderful day!