The first split in the Communist movement happened immediately upon its founding with a group of comrades in the Midwest forming the Proletarian Party led by Dennis Batt and John Keracher, leaving the first convention of the (old) Communist Party of America in September, 1919. Some of those original documents are found here.
The Proletarian, vol. 2, No. 6. October 1919.
Contents: Cover by V.M. Breitmayer, Spartacan Spark, Communist Party Convention by Oakley C. Johnson, Vaudeville Socialism by L.B., Morals vs. Profits by John O’London, The WILU Editor Bumps His Head Against the Proletarian by Oakley C. Johnson, Shall Private Property Be Abolished in America? by John Keracher, International Notes (England, Persia, Afghanistan, USA), As You Like It, Correspondence by John O’London, Revolutionary Political Action: The Road to Socialism, Manifesto and Program, Minority Report of the Committee on Manifesto and Program at the Communist Party Convention.
The monthly organ of the Proletarian Party of America, The Proletarian originally served a left wing faction in the Socialist Party of Michigan led by John Keracher, and was printed in Detroit and Chicago from May, 1918 until July, 1931. The Proletarian Party then published Proletarian News, from 1932 until 1960. Part of the early Communist movement, the Proletarian University and the Proletarian refused to join with others in going underground after the Palmer Raids, though it eschewed electoral politics. The Proletarian Party attempted to gain admittance to the Third International to no avail. The Party eventually took over the left wing publishing house Charles H. Kerr & Co.
Link to full issue PDF: https://www.marxists.org/history/usa/parties/ppa/1919/1000-proletarian-v02n06-opt.pdf