It can be easy to forget, between hot dogs, that your three-day weekend was actually the result of some of the most significant, lasting, and defining struggles in American history. The saga of American labor movements is as long and involved as it is explosive and filled with violence and ideology. But it's often chalked up to a strike here, or a protest there. Here are four important things to keep in mind about labor history on Labor Day.

Samuel Gompers

Let's start off not necessarily with a single moment, but a man responsible for many moments in American labor history. "Of all the days celebrated for one cause or another, there is not one which stands so conspicuously for social advancement of the common people as the first Monday in September," Samuel Gompers, a founder of the American Federation of Labor, wrote in a 1910 edition of the New York Times. As founder of the AFL, Gompers encapsulated labor sentiments of the time and ferried them to prominence with the organization, which became the largest labor federation in the world in his time as its president. Gompers was involved with many other labor organizations ever since joining a local chapter of the United Cigar Makers in New York, ultimately championing the 8-hour work day, benefits, and worker safety.

Haymarket Square Riot

The 1880s in America were a time of fervent protests for labor movements. Fed up with low pay, long hours and poor working conditions, and little representation to the massive corporations they worked for, workers—many of them immigrants—often took to the streets to make their voices heard. Chicago's Haymarket Square was the site of one such protest in May of 1886, when workers rallied in protest of police violence at a strike just one day before. The event may have fallen into obscurity had it not turned violent towards the end, when police arrived to disperse the crowd and a bomb was thrown into their midst, leading to gunfire between police and radical workers. As a result of the violence, eight radical labor activists were arrested and jailed, despite a lack of evidence. Some were even sentenced to death. The Haymarket riot is generally considered a setback in the labor movement, though it also served to create what some considered martyrs for the cause.

The Great Railroad Strike

The series of uncoordinated strikes in the summer of 1877 collectively known the Great Railroad Strike did not involve unions, but marked the first time federal troops had to be called in to halt labor protesters. This would later be echoed in the monumental Pullman strikes. Though the strikes began in Martinsburg, West Virginia, it soon spread to Cumberland, Maryland and Chicago after the Baltimore & Ohio Railroad company slashed workers' wages for a third time that year. Rail workers refused to run trains until the last cuts were revoked, cutting into both freight and passenger service. West Virginia Gov. Henry Mathews called in his state's militia to suppress worker demonstrations, but he was forced to call in federal reinforcements after his own troops refused to use force against the striking workers. In other cities, skirmishes between protesting laborers and National Guardsmen led to deaths and injuries, and also required national forces to calm things down. As historian Howard Zinn notes in his "A People's History of the United States," when the strikes were over, "a hundred people were dead, a thousand people had gone to jail, 100,000 workers had gone on strike, and the strikes had roused into action countless unemployed in the cities." Though the railroad company made some concession, Zinn writes, the strikes helped usher in tougher "'Coal and Iron Police,'" and may have helped lead to a realization that unorganized labor movements were not enough.

The Ludlow Massacre

Just over a century ago in April of 1914, violent conflict at the intersection of striking coal miners, union organizers, a powerful mining company, and the Colorado National Guard marked a turning point in American labor rights history. Roiled in a months-long, union-led struggle for for better pay and working conditions, union recognition, and loosened company control, workers and their families in Southern Colorado were forced to vacate their company-owned homes as punishment for striking, setting up a tent colony nearby. Tensions reached a breaking point when the state's national guard, along with camp guards attacked the camp, leaving dozens dead, including women and children who died in fires set by the militia. The incident sparked further violent miner-led protests at other mining sites run by several companies, including Rockefeller-owned Colorado Fuel & Iron Company, the Rocky Mountain Fuel Company, and the Victor-American Fuel Company. This sparked a national outcry that gave way to federal investigations into mine workers conditions and to modern day standards of employment, such as laws governing child labor and eight-hour work days. Although it is sometimes buried in discussions of labor movements, the massacre, as the New Yorker's Ben Mauk wrote, "changed the nation's attitude toward labor and capital for the next several decades."