May Revolution
The May Revolution was a direct reaction to Spain's Peninsular War. In 1808, King Ferdinand VII of Spain abdicated in favor of Napoleon, who granted the throne to his brother, Joseph Bonaparte. A Supreme Central Junta led resistance to Joseph's government and the French occupation of Spain, but eventually suffered a series of reversals that resulted in the Spanish loss of the northern half of the country. On February 1, 1810, French troops took Seville and gained control of most of Andalusia. The Supreme Junta retreated to Cadiz and dissolved itself, and the Council of Regency of Spain and the Indies replaced it. News of these events arrived in Buenos Aires on May 18, brought by British ships.
May Day riots of 1894
May Day, or International Workers' Day was a day for remembering the workers who died during the Haymarket affair of 1886. During a General Strike in Chicago, Illinois, an unknown person threw a bomb into the crowd, prompting police to fire into the crowd, killing civilians and police alike. The same day in 1890, Raymond Lavigne called for international demonstrations to commemorate the day. In 1894 the Pullman Strike in Illinois, as well as this series of unemployed workers' riots on May Day in Cleveland, prompted U.S. President Grover Cleveland to propose a bill that would make a Labor Day a national public holiday. After the Haymarket Square riot in May, 1886, US President Grover Cleveland 
feared that commemorating Labor Day on May 1 could become an opportunity to commemorate the riots. May Day celebrations have diminished in the United States, because of the creation of Labor Day.