Labor Day was promoted by the Central Labor Union and the Knights of Labor, who organized the first parade in New York City. After the Haymarket Massacre, which occurred in Chicago on May 4, 1886, U.S. President Grover Cleveland feared that commemorating Labor Day on May 1 could become an opportunity to commemorate the affair. Thus, in 1887, it was established as an official holiday in September to support the Labor Day that the Knights favored.
The equivalent holiday in Canada, Labour Day, is also celebrated on the first Monday of September. In many other countries (more than 80 worldwide), “Labour Day” is synonymous with, or linked with, International Workers’ Day, which occurs on May 1.