Farnum was born in Saginaw, Michigan and raised in a farm community at Watrousville.

He engaged in union activities ranging from shop steward to international representative for United Auto Workers-Congress of Industrial Organizations from 1942 to 1952.

He was an unsuccessful candidate for reelection in 1966, losing in the general election to Republican Jack McDonald.

[1] Farnum was a deputy chairman of the Democratic National Committee from 1967 to 1968 and a member of the Waterford Board of Education from 1969 to 1970.

The Michigan Senate's previous office building in Lansing was named after Farnum.