1) Labor unions began forming in the early 1800s but did not gain significant membership until the 1860s-1870s due to harsh working conditions during industrialization.
2) Two major early unions were the Knights of Labor, founded in 1869, which advocated for broad reforms, and the American Federation of Labor (AFL), founded in 1886, which focused on practical wage and hour issues for skilled workers.
3) Violent strikes in the 1870s-1890s undermined public support for unions and gave companies legal tools to resist organizing, weakening the labor movement for decades until reforms of the 1930s.