Located just across the Monongahela River from Pittsburgh, Carnegie Steel’s sprawling Homestead steel plant was the scene of a brutal battle between the Amalgamated Association of Iron and Steel Workers and the company’s chief executive, Henry Clay Frick, who wanted to break the union’s power.

In June 1892, Frick announced pay cuts for Homestead steelworkers and refused to negotiate with the union, instead locking workers out of the plant. Frick sent Pinkerton detectives on barges up the river in order to protect strikebreaking replacement workers he planned to hire. Pinkerton detectives had become known for infiltrating unions and breaking strikes nationwide, including at another Carnegie plant a few years earlier. When word spread of the Pinkertons' approach, thousands of striking workers and their families rushed to the river to keep them from coming ashore. The Pinkertons then became pinned down in a bloody gunfight with the strikers and were forced to surrender.

Eventually, the Pennsylvania State Militia was sent in to suppress the strike, and the union was crushed. But Frick nearly paid for the victory with his own life, surviving being shot and stabbed in an assassination attempt by anarchist Alexander Berkman. The Homestead strikers’ resolve inspired other unionists but also showed them how hard it would be to overcome a big company that had government support.

In 1893, George Pullman laid off three-quarters of his employees, cut wages for many of the ones he brought back by nearly 30 percent, and refused to reduce rents or store prices in the company town he operated south of Chicago. The following year, the American Railway Union, headed by Eugene V. Debs, announced a nationwide boycott of all trains carrying Pullman cars, to support the ARU local whose workers were employed by Pullman. The Pullman strike was the first instance in American labor history of a sympathy action, in which workers who aren’t directly involved in a dispute intervene to help fellow laborers.

The ARU managed to shut down rail travel in 27 states, an area stretching from Chicago to the West Coast, according to Indiana State University labor historian Richard Schneirov. But after Pullman’s company joined forces with railroad managers, President Grover Cleveland’s Attorney General Richard Olney convinced a federal judge to issue an injunction against the strikers, and Cleveland himself sent 10,000 federal troops in to suppress the strike. Most of the strikers eventually were rehired, except for union leaders who were blacklisted by Pullman. Debs served six months in prison for violating the injunction and used his time behind bars to read Karl Marx’s Das Kapital. After his release, he became active in the Socialist Party and ran five times for U.S. president.

When Massachusetts passed a law reducing the work week from 56 to 54 hours, factory owners tried to negate it by speeding up production and cutting workers’ wages. In Lawrence, Massachusetts, textile mill workers responded by shutting down their looms and walking out in what became known as the “Bread and Roses Strike.” About 25,000 immigrant workers from Ireland, Italy, Lithuania and other countries—most of them women— were pitted against mill owners, who expected a quick end to the dispute, according to Robert Forrant’s and Susan Grabski’s book on the strike.

When the AFL, mostly composed of white male skilled workers, wouldn’t help the Lawrence strikers, they turned to the more radical Industrial Workers of the World (IWW), who sent organizers and formed relief committees to provide food, medical care and other assistance. The strikers marched regularly by the thousands through the city’s commercial district, defying police and state militia sent to stop them. Some strikers began sending their children to live with supporters in other cities, and when authorities tried to stop some of them from boarding a train to Philadelphia, the resulting violent clash created plenty of bad publicity.

After Congress held hearings that exposed the awful working conditions in Lawrence, the owners finally were forced to the bargaining table, and in March 1912, workers voted to accept their offer. The strike not only was a major victory for the union movement but also established the importance of women and immigrants in organized labor.

During World War I, industrial companies, labor unions and the U.S. government joined together to form the War Labor Board, an organization that brokered a deal to stave off strikes in exchange for improved labor conditions. But the alliance was an uneasy one, and after the war ended in November 1918, the truce dissolved as well. A consortium of unions that included the American Federation of Labor and the Amalgamated Association of Iron, Steel and Tin Workers decided to challenge U.S. Steel, the nation’s biggest employer and one that refused to recognize unions, by calling a nationwide strike in September 1919, with 350,000 workers walking off the job in mills in six states.

While the strike temporarily paralyzed steel production, it eventually was crushed. Police and company-hired thugs beat up picketers, and tens of thousands of Black workers, who usually weren’t allowed to join unions because of racial prejudice, were brought in as strikebreakers. In January 1920, the AFL finally capitulated a defeat that was a setback for the labor movement.

In Flint, the year-old United Auto Workers union took on General Motors, one of the richest and most powerful companies on the planet, in a confrontation that was a transformational moment for the labor movement. Instead of walking off the job and giving management a chance to bring in non-union replacements, the auto workers unveiled a new tactic, the sit-down strike, in which they camped out inside the plant, making it impossible to resume production.

“If the company had tried to replace them, they would have had to engage in a one-on-one battle at each workstation,” explains Stepan-Morris. “And what replacement worker wants to do that?” Workers gambled, wrestled and played ping-pong on the factory floor, keeping it idle for 44 days. In January 1937, security guards and police stormed the plant, releasing tear gas, but workers fought back and held the plant in what became known as the ”Battle of the Running Bulls.”

Michigan Governor Frank Murphy, who had refused to intervene on behalf of GM, finally sent in the National Guard as peacekeepers, with orders not to use force against the strikers. Murphy eventually served as an intermediary in negotiations between GM and the union, who struck a deal in February 1937 that gave organized labor a major victory.

In California, newly-organized farm workers, led by Mexican American civil rights activist Cesar Chavez and Filipino American organizer Larry Itlion, fought a five-year struggle to get better pay and more humane working conditions. They accomplished that in part through nonviolent protest tactics such as marches and hunger strikes, but also tapped into public sympathy for their plight, by urging Americans to boycott grapes.

Eventually, the workers won a contract, and their long struggle also led to legislators enacting the California Agricultural Labor Relations Act of 1975, which gave collective bargaining power to farmworkers across the state.

In February 1968, two Black Memphis trash collectors were crushed to death by a malfunctioning truck compactor. Other Black sanitation workers were frustrated by the city’s refusal to compensate their families. They also saw it as part of a discriminatory pattern, in which they worked long days for just 65 cents per hour, with no overtime or paid sick leave. Defying an order from Memphis Mayor Henry Loeb III, 1,300 workers refused to collect trash, and more than 10,000 tons piled up.

The 1968 strike is also remembered as the backdrop for the assassination of civil rights icon Rev. Martin Luther King Jr., who was shot to death by a sniper while he was in the city supporting the strikers. After King’s widow Coretta Scott King led 40,000 people on a silent march through Memphis, the city finally agreed to raise workers’ salaries and recognize their union.

Employees of the U.S. Postal Department, the forerunner of the U.S. Postal Service, grew frustrated after years of low pay and few raises for the physically demanding job of processing and delivering the nation’s mail. They had little leverage because it was illegal for federal employees to strike. But in March 1970, postal workers in New York nevertheless went out on strike, defying their own union leadership, and soon workers elsewhere joined them in the largest-ever walkout by federal government employees.

Faced with a crisis, the administration of President Richard Nixon dispatched National Guard members to deliver the mail. After eight days, postal employees went back to work, and the Nixon administration gave them an immediate, retroactive pay hike. In 1971, when the USPS was formed, postal workers were given the right to negotiate salaries and working conditions.

After contract negotiations between the Federal Aviation Administration and the Professional Air Traffic Controllers Association (PATCO) broke down in the summer of 1981, nearly 13,000 air traffic controllers walked off the job. In response, President Ronald Reagan invoked a rarely-used law prohibiting government workers from striking and ordered the controllers to return to work. After only 10 percent of the workers complied, Reagan fired the rest and banned them from working for the government again. The union collapsed.

“The PATCO strike represented a shift in Federal government and corporate policy towards outright hostility to unions,” explains Louis M. Kyriakoudes, a professor of history at Middle Tennessee State University. PATCO’s defeat, along with other factors such as the migration of manufacturing from the Midwest and Northeast to union-hostile states in the South, helped drive organized labor in the United States into a sharp decline in membership.

In New York City’s Chinatown neighborhood, garment workers worked long days under often harsh conditions. But in 1982, after some employers tried to cut workers’ benefits and refused to sign with the International Ladies’ Garment Workers’ Union, nearly 20,000 workers—mostly Asian American women—went on strike.

“A lot of people just assumed that the women would not want to strike,” one organizer, Katie Quan, later recalled in an interview with NBC Asian America. “They had never attended meetings, and they certainly had never struck before.” But they did, and marched through Chinatown, calling for union recognition. Eventually, the owners who had been opposed to the union gave in. It was an important victory for the union and also led to greater recognition of women’s rights.