The massive bloody strike on 8 March 1857 of the female workers in the textile industries of New York who - demanding the reduction of the work hours to 10 hours per day, equal pay of men and women and health and safety conditions in the work places - were brutally attacked by the government and the employers, motivated the 2nd International Conference of the Socialist Women in Copenhagen in 1910 – held with the initiative of the great German communist Clara Zetkin - to call for the celebration of the 8 March as the International Day of Women:
http://www.wftucentral.org/wp-content/2012_03_05_statement_wftu_international-womens-day.pdf
