Some of the victims had been accused of murdering a police chief, but were acquitted after a trial.
Angry about the verdict, a mob of racist vigilantes in the city attacked and publicly hanged them.
Mayor LaToya Cantrell is due to apologise for the killing - believed to be the largest recorded lynching in US history - on 12 April.
She will issue the apology at an Italian-American cultural centre in the city, a spokesman told the Associated Press news agency.
What happened in 1891?