From http://www.u-s-history.com/pages/h750.html and http://www.digitalhistory.uh.edu/database/article_display.cfm?HHID=227
The growth of American industrial might in the 1870s and 1880s was paralleled by the emergence of unions representing the workers. Foremost among the early labor organizations was the Knights of Labor, which listed more than 700,000 members by the mid-1880s. Working conditions at the time were abysmal—little concern for safety existed in most factories, pay was low, benefits were nonexistent and the work day was often 10 to 12 hours, six days a week. The immediate focus of the K.O.L. and other unions was to achieve the eight-hour day.