[A] gunfight broke out between members of the Colorado National Guard and striking coal miners employed by the Colorado Fuel and Iron Company near Trinidad, Colorado. During the fighting in and around a tent encampment of striking miners, eleven children and two women were killed when the tent above a pit they were taking shelter from the fighting in was set on fire. This event became known as the Ludlow Massacre, and shocked the nation into a greater awareness of the poor working conditions and exploitative "company town" economic predation faced by coal miners.Today, all mine workers in the U.S. have a right to unionize and a very large percentage do (unlike the bulk of the private sector work force in which unionization is at pre-labor law lows), and safety standards in mining are much higher, mostly as a result of the Mine Safety and Health Administration which rivals the National Transportation Safety Board which regulated air and rail traffic safety, for its effectiveness (in stark contrast to the largely ineffectual (outside of manufacturing) Occupational Health and Safety Administration, OSHA, which has never had sufficient funding relative to its regulatory jurisdiction to make much of a difference).
The creation of a "company union" in the wake of the Ludlow massacre by Rockefeller's Colorado Fuel and Iron Company to prevent a real union with a more aggressive stance from filling the vacuum is one of the reasons that current U.S. law prohibits such unions which are common in places like Japan.
But, coal mining remains a very dangerous profession relative to most other professions even today. There are far more coal mining and transportation and power plant deaths than there are deaths from nuclear power to workers and non-workers alike, for example. In recent years, many of the reduced deaths are due to automation rather than improved safety standards. Abroad, for example in China, safety standards for miners are much lower and there are many deaths.
Worker's compensation, another aftermath of that era has been a mixed blessing, making some compensation for injured or killed workers almost automatic, but providing stingy amounts of compensation that are overrun with red tape.
I can't recall the last time that the National Guard was called upon in any state to put down union activity, and the Kent State shooting of war protesters in Ohio, on May 4, 1970, before I was born, is one of the last notable times the National Guard killed U.S. civilians, although the National Guard was called upon to provide civil security in the wake 9-11 at airports and has been called upon to deal with civil unrest now and then on many occasions, generally under the direction of state governors rather than when called up to federal duty when the Posse Comitatus Act (arguably one of the most important parts of the "unwritten constitution" in the United States) applies.
* It was also the day critical in the marijuana subculture, that evolved from a group of kids who smoked pot in California after school at that time in 1971, after which the number began to be associated with marijuana generally, and then morphed into a month and day instead of an hour and minute. One of the biggest events honoring this date in the Denver area was the Cannabis Cup at the Denver Merchandise Mart organized by High Times magazine, which had thousands of visitors paying $40 or so a head to get into to see the vendors and events. It was the 40th time the event was held and the first in a state with legalized recreational marijuana. The crowd was well behaved and there were few incidents of note.
* It was also Hitler's birthday,
* And, this year, it was Easter. Incidentally, one of the main historical investments of the Roman Catholic Church in astronomy (which continues to this day) originally involved the effort to correctly determine the date of Easter. The Vatican observatory is one of the reasons that this Christian denomination embraces the Big Bang and an allegorical, rather than literal, reading of the creation story in the Bible.