Johnson was the son of a longshoreman and a seamstress, and began working as a stevedore at the age of 17.
A Marine during World War II, Johnson was wounded at the Battle of Iwo Jima in 1945.
In the same year, he organized slates of delegates to run against Tammany Hall leaders, whom he accused of corruption; Johnson himself ran against Greenwich Village's Democratic district leader, Carmine DeSapio, described as "Tammany's chieftain".
[3] Neither the strike nor the political campaign produced immediate results, but they led to a subsequent purge of the union's leadership and to Tammany's adopting a more open mode of selecting its district leaders.
He advised New York Governor Mario Cuomo, and served on mayoral commissions on justice and healthcare.