Marks was born in Ventersdorp in 1903. His father was a railway worker and his mother a midwife. He attended Kilnerton Teacher's Training Institute in Pretoria. In 1932 he was elected to the Central Committee of the Communist Party of South Africa (CPSA) and was ater appointed President of the Transvaaal ANC. In 1942 Marks was elected to the position of President of the Transvaal Council of Non-European Trade Unions and in the same year to presidency of the African Mineworkers' Union. He was deeply involved in the 1946 African mineworkers strike. Marks went into exile in the Soviet Union in the early 1960s but continued to serve on the national executive committee of the ANC and the newly named South African Communist Party (SACP) of which he was chairman. After he died he was buried in the Hero's Acre at Novodevichy cemetary in Moscow, but in March 2015 his remains were repatriated to South Africa and he was reburied at his home in Ventersdorp.