Beginning in the late 19th century, as the trade union and labour movements grew, a variety of days were chosen by trade unionists as a day to celebrate labour. 1 May was chosen to be International Workers' Day to commemorate the 1886 Haymarket affair in Chicago. In that year beginning on 1 May, there was a general strike for the eight-hour workday. On 4 May, the police acted to disperse a public assembly in support of the strike when an unidentified person threw a bomb. The police responded by firing on the workers. The event led to the deaths of seven police officers and at least four civilians; sixty police officers were injured, as were an unknown number of civilians. Hundreds of labour leaders and sympathizers were later rounded-up and four were executed by hanging, after a trial that was seen as a miscarriage of justice.[nb 1] The following day on 5 May in Milwaukee Wisconsin, the state militia fired on a crowd of strikers killing seven, including a schoolboy and a man feeding chickens in his yard.
In 1889, a meeting in Paris was held by the first congress of the Second International, following a proposal by Raymond Lavigne that called for international demonstrations on the 1890 anniversary of the Chicago protests. May Day was formally recognized as an annual event at the International's second congress in 1891. Subsequently, the May Day riots of 1894 occurred. The International Socialist Congress, Amsterdam 1904 called on "all Social Democratic Party organisations and trade unions of all countries to demonstrate energetically on the First of May for the legal establishment of the 8-hour day, for the class demands of the proletariat, and for universal peace." The congress made it "mandatory upon the proletarian organisations of all countries to stop work on 1 May, wherever it is possible without injury to the workers."
In the United States and Canada, a September holiday, called Labor or Labour Day, was first proposed in the 1880s. In 1882, Matthew Maguire, a machinist, first proposed a Labor Day holiday on the first Monday of September[nb 2] while serving as secretary of the Central Labor Union (CLU) of New York. Others argue that it was first proposed by Peter J. McGuire of the American Federation of Labor in May 1882, after witnessing the annual labour festival held in Toronto, Canada. In 1887, Oregon was the first state of the United States to make it an official public holiday. By the time it became an official federal holiday in 1894, thirty US states officially celebrated Labor Day. Thus by 1887 in North America, Labour Day was an established, official holiday but in September, not on 1 May.
May Day has been a focal point for demonstrations by various socialist, communist and anarchist groups since the Second International. May Day is one of the most important holidays in communist countries such as the North Korea, Cuba and the former Soviet Union countries. May Day celebrations in these countries typically feature elaborate workforce parades, including displays of military hardware and soldiers.
In 1955, the Catholic Church dedicated 1 May to "Saint Joseph the Worker". Saint Joseph is the patron saint of workers and craftsmen, among others.
During the Cold War, May Day became the occasion for large military parades in Red Square by the Soviet Union and attended by the top leaders of the Kremlin, especially the Politburo, atop Lenin's Mausoleum. It became an enduring symbol of that period.
Today, the majority of countries around the world celebrate a workers' day on 1 May.