He attended Mississippi State University where he received a bachelor's degree in Agricultural Economics in 1977.

He was vice president of McCullough Steel Products, Inc. and served on the staff of Mississippi Governor Kirk Fordice.

During his tenure with TVA, the utility earned national recognition for its economic development efforts and launched its megasite program.

McCullough was a candidate for the U.S. House of Representatives when the seat became vacant due to the appointment of Congressman Roger Wicker to the United States Senate.

[8] In May 2015, McCullough was appointed by Governor Phil Bryant as the executive director of the Mississippi Development Authority.