The WPUS was formed in 1876, when a congress of socialists from around the United States met in Philadelphia in an attempt to unify their political power. Seven societies sent representatives, and within four days the party was formed under the name of the Workingmen's Party of the United States. The party, composed mostly of foreign-born laborers, represented a collection of socialist ideas from different groups, most notably followers of Karl Marx and Ferdinand Lassalle. The Lassallean faction believed in forming a Socialist political party to advance their agenda incrementally through the electoral process. Marxian Socialists, however, opposed to reformism believed in forming a Socialist party as an instrument of organization of the proletariat to propagate consciousness leading to an ultimate revolutionary seizing of state power. They championed strong trade unions, strikes, and boycotts to develop class consciousness through class conflict.
The party at first had little influence over any politics in the United States on a national or local level. Much like the International Workingmen's Association before it, the WPUS was widely viewed as socialistic. However, during the railroad strikes during the summer of 1877, the party, led by the charismatic and well-spoken American Albert Parsons, showed some of its power by rallying support for the striking railroad workers.
Although the WPUS was largely unsuccessful in the strikes it helped lead, on August 6, 1878 the party had managed to gain enough popularity to capture 5 out of 7 seats in Kentucky state legislature. As news spread around the country of the success of the WPUS, more "Workingmen's Parties" formed in cities around the country, some chartered by the WPUS and some not.
The end of the Workingmen's Party of the United States came in December 1878, when it reformed as the Socialist Labor Party.