The International Socialists group was founded out of the US Independent Socialist Clubs in 1969. The US International Socialists (IS) had chosen the name due to their contact with the British International Socialists group.
In 1973, the Revolutionary Tendency of the IS was expelled. The Revolutionary Tendency had felt that the IS was going too easy on the labor reformers the IS was working with. The Revolutionary Tendency would go on to form the Revolutionary Socialist League.
By the late 1970's, the IS was very involved in trade union work. The British International Socialists, who in 1977 began calling themselves the Socialist Workers Party (SWP/UK), disagreed with the strategy the US International Socialists were using. A faction within the IS/USA agreed with the SWP/UK and were expelled in 1977. This faction would go on to from the International Socialist Organization.