According to Bureau of Labor Statistics (BLS) provisional estimates, in July 2003 the seasonally adjusted civilian labor force in Pennsylvania numbered 6,195,200, with approximately 347,800 workers unemployed, yielding an unemployment rate of 5.6%, compared to the national average of 6.2% for the same period. Since the beginning of the BLS data series in 1978, the highest unemployment rate recorded was 13.1% in February 1983. The historical low was 4.0% in April 2000. It is estimated that in 2001, 4.5% of the labor force was employed in construction; 16.2% in manufacturing; 5.6% in transportation, communications, and public utilities; 19.0% in trade; 5.9% in finance, insurance, and real estate; 28.7% in services; 11.4% in government; and 1.7% in agriculture.

The history of unionism in Pennsylvania dates back to 1724 when Philadelphia workers organized the Carpenters' Company, the first crafts association in the colonies. Its Carpenters' Hall gained fame as the site of the First Continental Congress in 1774; the carpenters were also responsible for the first strike in the United States in 1791. The nation's first labor union was organized by Philadelphia shoemakers in 1794. By 1827, the Mechanics' Union of Trade Associations, the country's first central labor body, was striking for a 10-hour workday and was the impetus behind the formation of the Organized Workingman's Party. Nine years later there were no fewer than 58 labor organizations in Philadelphia and 13 in Pittsburgh, but the Panic of 1837 resulted in a sharp decline of union strength and membership for many years. Union ranks were further depleted by the Civil War, despite the efforts of Pennsylvania labor leader William Sylvis, who later became an important figure in the national labor reform movement. After the Civil War ended, the Noble Order of the Knights of Labor was established in Philadelphia in 1869.

The coal fields were sites of violent organizing struggles. In 1835, low wages and long hours sparked the first general mine strikes, which, like a walkout by anthracite miners in 1849, proved unsuccessful. During the 1850s and 1870s, a secret society known as the Molly Maguires led uprisings in the anthracite fields, but its influence ended after the conviction of its leaders for terrorist activities. The demise of the Molly Maguires did not stop the violence, however. Eleven persons were killed during a mine strike at Connellsville in 1891, and a strike by Luzerne County miners in 1897 resulted in 20 deaths. Finally, a five-month walkout by anthracite miners in 1902 led to increased pay, reduced hours, and an agreement to employ arbitration to settle disputes.

Steelworkers, burdened for many years by 12-hour workdays and 7-day workweeks, called several major strikes during this period. An 1892 lockout at Andrew Carnegie's Homestead steel mill led to a clash between workers and Pinkerton guards hired by the company; after several months, the strikers went back to work, their resources exhausted. A major strike in 1919, involving half of the nation's steelworkers, shut down the industry for more than three months, but it too produced no immediate gains. The Steel Workers Organizing Committee, later the United Steelworkers, finally won a contract and improved benefits from US Steel in 1937, although other steel companies held out until the early 1940s, when the Supreme Court forced recognition of the union.

The US Department of Labor reported that in 2002, 847,000 of Pennsylvania's 5,452,000 employed wage and salary workers were members of unions. This represented 15.5% of those so employed, down from 17.0% in 2001. The national average is 13.2%. In all, 907,000 workers (16.6%) were represented by unions. In addition to union members, this category includes workers who report no union affiliation but whose jobs are covered by a union contract. The most important union in the state is the United Steelworkers of America, headquartered in Pittsburgh.