In 1842, the Suffolk County Attorney filed an indictment against the Boston Journeyman Bootmaker’s Society alleging that the organization was a criminal conspiracy. The society had organized several strikes in the 1830s in an effort to achieve higher wages for its members. The Massachusetts Supreme Court ruled that labor combinations are legal provided that they are organized for a legal purpose and use legal means to achieve their goals. This case set an important precedent.

Founded in 1866, the National Labor Union created a national federation of labor organizations, including skilled and unskilled workers. It pressed for an eight-hour work day along with other reforms. Several hundred thousand members joined the organization prior to its collapse in 1873.

The Molly Maguires was a secret society with members ranging from Ireland to Liverpool and eastern Pennsylvania in the US. The society focused on helping Irish natives to deal with unfair treatment. In 1877, following a series of violent conflicts, 20 members of the Molly Maguires were convicted of murder and other crimes and were executed by hanging.

The Great Railroad Strike of 1877 began in Martinsburg, West Virginia. Workers went on strike against the Baltimore & Ohio Railroad after their wages were cut for the third time in a year. The strike grew to include more than 100,000 workers from New York, Pennsylvania, Maryland, Illinois, and Missouri. A combination of a state militia and federal troops clashed with strikers, culminating in a death toll surpassing 100 people.

The labor demonstration at Haymarket Square in Chicago began peacefully on May 4, 1886. However, as police dispersed the crowd, an unknown individual threw a bomb. The explosion killed seven policemen. Gunfire erupted and four civilians were also killed. In response to the riot, officials further clamped down on labor unions, and eight anarchists were eventually convicted for the attack.

Formed in 1869, the Knights of Labor accrued nearly 800,000 members by 1886. The Knights' primary demand was for an eight-hour work day, but they also called for legislation to end child labor. Their organizational structure was weak, and after the Haymarket riot there was a political backlash against U.S. labor organizations. Most of its members abandoned the organization by 1890.

Born in London in 1850, Samuel Gompers and his family emigrated to American in 1863. He became a cigar maker and then founded the AFL in 1886. He served as the organization's president until he died in 1924.

The American Railway Union launched a strike against the Pullman Company in 1894 primarily in response to reduced wages. It began as a small, unionized strike lacking the support or approval of a leader, but eventually spread to include 250,000 workers in 27 states. After the death of 30 people and over $80 million in property damages, the army was called in to quash the strike. In an effort to appease the trade unions and work towards reconciliation, Congress approved Labor Day and declared it a national holiday.

Born in Ireland in 1837, “Mother” Jones emigrated to Canada and then the United states. She became a labor activist, focusing on labor representation and community organization. She facilitated many major strikes in addition to co-founding the Industrial Workers of the World. She was jailed several times and was denounced as the “grandmother of all agitators.”

In 1902, the United Mine Workers of America launched a strike in Pennsylvania. President Teddy Roosevelt intervened and helped negotiate an agreement. The miners bargained for a pay increase and a shorter work week while mine owners received an increased price for coal.

Born in Salt Lake City in 1869, William “Big Bill” Haywood became a miner at a young age. He was a founding member and leader of the IWW. He saw industrial unionism, organizing all workers in an industry under the same union, as the best way to maintain leverage during potential strikes. He was convicted of opposing the draft during World War I and fled to Russia as a result. He died in 1928.

In 1921, Coal miners in West Virginia attempted to form a union. Mine owners resisted the effort, which culminated in an armed conflict between 10,000 miners and 3,000 police and strikebreakers. President Warren G. Harding authorized bombers to conduct aerial surveillance. The miners finally disbanded after federal troops arrived. Approximately 100 people were killed in the conflict and 985 miners were arrested.

Lewis served as president of the United Mine Workers of America from 1920 to 1960. During his tenure as president of the UMWA, he also formed the Congress of Industrial Organizations (CIO) in 1935. The CIO helped to organize millions of industrial workers; in 1955, it merged with the American Federation of Labor.

Previously, workers on strike organized protests outside of factories. During the 1930s, sit-down strikes became more common, whereby workers entered factories and occupied facilities. This tactic easily brought production to a halt while giving the strikers more bargaining power.

President Franklin D. Roosevelt signed the National Labor Relations Act in 1935, which is often called the Wagner Act. This Act guarantees the right of private sector employees to unionize, engage in collective bargaining, take collective action, and to strike if necessary. It also established the National Labor Relations Board, which supervises labor union elections and investigates unfair labor practices.

President Franklin D. Roosevelt signed the Fair Labor Standards Act in 1938. The bill established a minimum wage of 40 cents per hour and guaranteed “time-and-a-half” for most jobs if workers clocked more than 40 hours per week.

The Taft-Hartley Act of 1947 amended the Wagner Act of 1935. President Harry S. Truman vetoed the bill, but Congress overrode his veto. The law restricts union activity and bans the use of

The AFL was founded in 1886, and the CIO was founded in 1935. The two organizations were fierce rivals during the 1930s, but found it preferable to merge in 1955.

Chavez was born in Arizona in 1927. He dropped out of school in the 7th grade to become a migrant farmer worker. In 1962, he co-founded the National Farm Workers Association with Dolores Huerta. It was later called the United Farm Workers of America (UFW). The UFW organized boycotts and strikes in order to achieve higher pay and additional rights for farm workers and eventually transitioned into a union and became the United Farmworkers Union.

Several hundred high school and college students in New York City protested shootings that took place at Kent State University, which killed 4 students. Many union members supported the war and they clashed with the anti-war protestors. At least 70 people were injured.

A wildcat strike is a strike undertaken by unionized workers without the authorization, support, or approval of the union’s leaders. Although it was illegal for federal employees to do so, postal workers went on strike for two weeks in 1970. During the strike, President Nixon ordered 24,000 military personnel to distribute the mail. The strike ultimately led to a reorganization of the postal service.

The Professional Air Traffic Controllers Organization was founded in 1968. In 1981, the union launched a strike and demanded both better pay and working conditions. However, it was illegal for federal employees to go on strike. President Ronald Reagan fired more than 11,000 controllers who refused to return to work. Historian Joseph McCartin has described the union’s defeat as “one of the most important events in late twentieth century U.S. labor history.”

Between 1995 and 1999, the NBA experienced three lockouts and a fourth occurred in 2011. The NHL has also had labor disputes in 1992, 1994–95, 2004–2005, and 2012–2013. The NFL has had eight labor disputes between 1968 and 2012.

As of 2016, 26 states have passed “right to work” laws, which prevent workers from being forced to join a union or pay union dues.

Union membership peaked in 1954 at 28.3% of the workforce, but has now fallen to 11.1%. There is substantial debate over the causes of this decline. Some possible explanations include: