The first "National Woman's Day" was organized on February 28, 1909 in New York by the Socialist Party of America.
In subsequent years the idea spread to European countries, namely to Austria, Denmark, Germany and Switzerland, after participants of a 1910 International Socialist Women's Conference in Copenhagen, Denmark, inspired by their US associates proposed the establishment of an annual Women's Day.
Women's Day in Russia
Russian women went further and their march in 1917 in the capital of the then Russian Empire, Petrograd was the beginning of the February Russian Revolution. A strike for "Bread and Peace": the end of World War I, end of food shortages in the country, and the end of czarism led to mass strike and the czar's later demise.
After the October Revolution, the Bolsheviks Vladimir Lenin and Alexandra Kollontai proclaimed this day an official holiday in the Soviet Union.
The United Nations started celebrating International Women's Day in International Women's Year in 1975. Two years after, the United Nations General Assembly urged member states to declare March 8 as the UN Day for women's rights and world peace.