The two-year effort to end racial segregation in Louisville businesses has been commemorated with a historical plaque downtown.The marker stands at 4th and Chestnut streets. The thoroughfare was a crowded business district in 1961, when local students began nonviolent protests against Jim Crow laws. The NAACP and the Congress of Racial Equality joined the efforts.A campaign of boycotts, demonstrations, arrests and voter-registration drives led to the passage of an ordinance in 1963 banning discrimination based on race, color, religion and nationality in public places.The historical marker outlines the struggle. It was sponsored by the local chapter of the NAACP and dedicated this weekend.