The person who possibly had the greatest impact for civil rights during the Jim Crow era was Martin Luther King Jr.
MLK was so effective in working towards civil rights because he advocated in nonviolent protests and made people follow alongside him, making their cause to other Americans who were not impacted by Jim Crow directly feel for the cause. The way MLK spoke was also integral, as in his speeches he showed that he truly believed in his cause and he spoke in a manner that made people relate, sympathize, motivate, and inspire. He was so great at speaking and giving speeches, that still many years later, his speeches are the most engaged with of his period.
There are many other leaders of the civil rights movement, and many who opposed it too, however, Martin Luther King Jr's vision and dreams have shined the brightest, still resonating and impacting many in the present time.