Chiefs CEO Clark Hunt issued a statement on Sunday: "My entire family is deeply saddened to learn of the passing of Jack Steadman. Jack was more than a dedicated and talented businessman, but a dear friend to my family. He was one of my father (Lamar's) greatest business associates and the two of them accomplished much during the more than four decades they worked together.
"I had the privilege of knowing Jack my entire life, and he taught me much about both business and life. He always brought a strong, innovative perspective to the room. Jack was an outstanding man of character, who greatly valued his faith and family."
Steadman had been dealing with Alzheimer's disease in recent years.
He was credited with conceiving the side-by-side stadium layout at the Truman Sports Complex, home to Arrowhead Stadium and the Kansas City Royals' Kauffman Stadium.
"Next to my father Lamar, no single person has had a greater impact on the Chiefs organization than Jack Steadman," Clark said in 2007 after Steadman stepped away. "For nearly six decades, he has tirelessly supported our family serving as the driving force behind almost every major initiative undertaken in that time."
Steadman and Lamar also had successful business ventures together -- Worlds of Fun, a 165-acre family entertainment complex, as well as Hunt Midwest Enterprises -- that helped build the Kansas City community.
"It's been a long journey, but we developed what we thought was a foundation for success and just kept working at it," Steadman said in 2005. "It took a lot of civic and political help before we finally achieved success. Unfortunately, we haven't achieved all the Super Bowl success we wanted, but we did win three AFL championships while I was general manager."