Marsh's family moved to Alabama when he was five and he grew up in East Lake, where his father sold cars. He graduated from Banks High School and then Auburn University to study industrial management. He started his first company, Sport Lines, near campus, detailing cars. He met his wife, Ginger, there, and moved to Calhoun County to work for his new father-in-law's Industrial Plating Company. He bought the firm in 1988 and diversified with Aerospace Coatings, which refurbishes aircraft parts for customers worldwide.
Marsh, a Republican, was first elected to represent the 12th District in the State Senate in the 1998 election, defeating incumbent Democrat Doug Ghee. He was re-elected in 2002, 2006, and 2010. In 2011 his colleagues elected him president pro tempore, with responsibility for assigning bills to committee. In facing chronic budget shortfalls, Marsh has made "critical state functions" such as programs that help seniors, children and people with disabilities his priority, at the expense of arts programs and bloated agencies.
- Lockette, Tim (February 27, 2011) "Del Marsh ready to turn business principles loose in political arena" Anniston Star
- Chandler, Kim (February 27, 2011) "Alabama Legislature: Pro-business agenda predicted by Senate pro tem Del Marsh." Birmingham News
- Del Marsh at legislature.state.al.us/senate