The Knights of Labor organized strikes against Jay Gould's southwest railroad system in 1884 and 1886, according to the History Channel's website. An article archived on the New York Times website from March 29, 1886, points out that the reason for the latter strike was that Gould mistreated 15,000 out of 18,000 of the workers employed by his railroad by paying them "slave wages" for their work.
Mistreating his workers by paying them poverty-level wages was not Jay Gould's only misdeed in his career in business. An article on About.com on 19th century history says that though he was one of the richest men in America, he was also the most despised. He began his career in business by manipulating stocks on Wall Street, protecting his illegal practices by bribing judges and politicians. He got into the railroad business in 1867, when he successfully wrested control of the Erie Railroad from Cornelius Vanderbilt. In 1869, his scheme to corner the gold market in America caused a massive panic on Wall Street, culminating in "Black Friday," a major economic disruption through which Gould made millions.
In 1872, Gould lost the Erie Railroad, but he bought up massive amounts of other railroad stock, as well as the Manhattan Elevated Railroad, until he was a dominating force in the transportation infrastructure of the country. Unscrupulous and ruthless until the end, he died in December 1892, having accumulated a fortune worth around $100 million.