United Mine Workers of America in the context of "Knights of Labor"

Americanization is the process of an immigrant to the United States becoming a person who shares American culture, values, beliefs, and customs by assimilating into the American nation. This process typically involves learning the American English language and adjusting to American culture, values, and customs. It can be considered another form of, or an American subset of Anglicization.

The Americanization movement was a nationwide organized effort in the 1910s to bring millions of recent immigrants into the American cultural system. 30+ states passed laws requiring Americanization programs; in hundreds of cities the chamber of commerce organized classes in English language and American civics; many factories cooperated. Over 3000 school boards, especially in the Northeast and Midwest, operated after-school and Saturday classes. Labor unions, especially the coal miners, (United Mine Workers of America) helped their members take out citizenship papers. In the cities, the YMCA and YWCA were especially active, as were the organization of descendants of the founding generation such as the Daughters of the American Revolution. The movement climaxed during World War I, as eligible young immigrant men were drafted into the Army, and the nation made every effort to integrate the European ethnic groups into the national identity.

The Ludlow Massacre was a mass killing perpetrated by anti-striker militia during the Colorado Coalfield War. Soldiers from the Colorado National Guard and private guards employed by Colorado Fuel and Iron Company (CF&I) attacked a tent colony of roughly 1,200 striking coal miners and their families in Ludlow, Colorado, on April 20, 1914. Approximately 21 people were killed, primarily miners' wives and children. John D. Rockefeller Jr. was a part-owner of CF&I who had recently appeared before a United States congressional hearing on the strikes, and he was widely blamed for having orchestrated the massacre.

The massacre was the seminal event of the 1913–1914 Colorado Coalfield War, which began with a general United Mine Workers of America strike against poor labor conditions in CF&I's southern Colorado coal mines. The strike was organized by miners working for the Rocky Mountain Fuel Company and Victor-American Fuel Company. Ludlow was the deadliest single incident during the Colorado Coalfield War and spurred a ten-day period of heightened violence throughout Colorado. In retaliation for the massacre at Ludlow, bands of armed miners attacked dozens of anti-union establishments, destroying property and engaging in several skirmishes with the Colorado National Guard along a 225-mile (362 km) front from Trinidad to Louisville. From the strike's beginning in September 1913 to intervention by federal soldiers under President Woodrow Wilson's orders on April 29, 1914, an estimated 69 to 199 people were killed during the strike. Historian Thomas G. Andrews declared it the "deadliest strike in the history of the United States."

The Colorado Coalfield War was a major labor uprising in the southern and central Colorado Front Range between September 1913 and December 1914. Striking began in late summer 1913, organized by the United Mine Workers of America (UMWA) against the Rockefeller-owned Colorado Fuel and Iron (CF&I) after years of deadly working conditions and low pay. The strike was marred by both targeted and indiscriminate attacks from both strikers and individuals hired by CF&I to defend its property. Fighting was focused in the southern coal-mining counties of Las Animas and Huerfano, where the Colorado and Southern railroad passed through Trinidad and Walsenburg. It followed the 1912 Northern Colorado Coalfield Strikes.

Tensions climaxed at the Ludlow Colony, a tent city occupied by about 1,200 striking coal miners and their families, in the Ludlow Massacre on 20 April 1914 when the Colorado National Guard attacked. In retaliation, armed miners attacked dozens of mines and other targets over the next ten days, killing strikebreakers, destroying property, and engaging in several skirmishes with the National Guard along a 225-mile (362 km) front from Trinidad to Louisville, north of Denver. Violence largely ended following the arrival of federal soldiers in late April 1914, but the strike did not end until December 1914. No concessions were made to the strikers. An estimated 69 to 199 people died during the strike, though the total dead counted in official local government records and contemporary news reports is far lower. The labor dispute was the bloodiest in the United States and Colorado historian William J. Convery called it the "bloodiest civil insurrection in American history since the Civil War." The Colorado Coalfield War is notable for the number of company-aligned dead in a period when strikebreaking violence typically saw fatalities exclusively among strikers, and contributed to the rapid escalation of violence in the later Battle of Blair Mountain.