Born in Waterville, Maine in 1928, Robert A. Marden was graduated from Waterville High School and Colby College. He received his LL.B. from Boston University School of Law.
A member of the Waterville City Council in 1952 and 1953, Marden was County Attorney for Kennebec form 1957 to 1960.
Elected to the Maine State Senate in 1961 he was reelected in 1963, serving as President of that body in the latter term.
Following his term as Senate President, Marden returned to his private law firm in Waterville.