Hall was born Arvo Kustaa Halberg in 1910 in Cherry Township, a rural community on northern Minnesota's Mesabi Iron Range. He was the son of Matt (Matti) and Susan (Susanna) Halberg. Hall's parents were Finnish immigrants from the Lapua region, and were politically radical: they were involved in the Industrial Workers of the World (IWW) and were early members of the Communist Party USA (CPUSA) in 1919. The Mesabi Range was one of the most important immigration settlements for Finns, who were often active in labor militancy and political activism. Hall's home language was Finnish, and he conversed with his nine siblings in that language for the rest of his life. He did not know political terminology in Finnish and used mostly English when meeting with visiting Finnish Communists.