after passage, the fifteenth amendment did not have much of any impact on black voting in the south for nearly a century. southerners used various methods including terrorism, poll taxes and grandfather clauses to prevent blacks from voting. congress and the supreme court repeatedly struck down voting restrictions. for example, in a landmark decision in "smith v. allwright" (1944), the court decision made it unconstitutional to keep african-americans from voting in a democratic party primary in texas. congress passed the civil rights act of 1957 which stated that all americans had the right to vote, including african-americans. but overcoming these problems on a case-by-case basis was proving to be unsuccessful. as soon as one form of discrimination was stopped, a new one appeared in its place. the voting rights act of 1965, removed further barriers to minorities voting. it was amended five times by congress to extend its protections as needed.