The Knights of Labor (K of L), officially the Noble and Holy Order of the Knights of Labor, was the largest American labor movement of the 19th century, claiming for a time nearly one million members. It operated in the United States as well in Canada, and had chapters also in Great Britain and Australia. Terence V. Powderly was one of the most notable leaders of the organization as he was the leader during its rapid rise and decline. The Knights of Labor promoted the social and cultural uplift of the worker, and demanded the eight-hour day. In some cases it acted as a labor union, negotiating with employers, but it was never well organized or funded. It was notable in its ambition to organize across lines of gender and race and in the inclusion of both skilled and unskilled labor. It grouped all workers, regardless of occupation, into a single body. After a rapid expansion in the mid-1880s, it suddenly lost its new members and succumbed to a jurisdictional battle with the new American Federation of Labor. The Knights of Labor had served as the first mass organization of the working class in the United States.
Founded by Uriah Stephens on December 28, 1869, the Knights of Labor reached 28,000 members in 1880, and 100,000 in 1884. By 1886, it had nearly 800,000 members: 20% of all workers. Its frail organizational structure could not cope as charges of failure, violence, allegations, and backlash following the 1886 Haymarket Square riot battered it. Most members abandoned the movement in 1886–1887, leaving at most 100,000 members in 1890. Many opted to join groups that helped to identify their specific needs instead of the KOL which addressed many different types of issues. The Panic of 1893, the largest economic depression in US history at the time, ended the Knights of Labor's importance. While their national headquarters closed in 1917, remnants of the Knights of Labor survived until 1949, when the group's last 50-member local dropped its affiliation.