David is a fourth generation Iowa farmer, growing corn, hay, and soybeans on his fifth generation family farm in Glenwood. He attended Iowa Western Community College and as well as Iowa State University. He is also a licensed real estate agent and works for Jim Hughes Real Estate.

Along with his work in agriculture, Sieck has passionately pursued opportunities in renewable energy and economic development. This includes being a founding board member of both Southwest Iowa Renewable Energy (SIRE) and Western Iowa Energy.

David is a past president of the Iowa Corn Growers Association and past committee member of the National Corn Growers Association. He has also served as the Vice Chairman of the Missouri River Recovery Implementation Committee. He is also an active community volunteer as a member of the Glenwood Optimists and Mills County Economic Development Foundation.

Sieck and his wife, Kim, have been married for 31 years and have three children; Maddison, Evan, and Alexa. The family attends St. John's Lutheran Church in Council Bluffs.