[3] He received a doctorate in blood pathology from Stritch School of Medicine at Loyola University Chicago in 1975, and engaged in seven years of post-doctoral study, specializing in the laboratory diagnosis of lymphoma and leukemia.
In 1993, he sold DeYor Laboratories to Corning Inc.[5] York has made a number of contributions in the medical field, having given a $1.5 million contribution to establish an Endowed Chair in Pathology and an Endowed Chief Residency in Pathology at the University of Arkansas for Medical Sciences.
In 1999, he donated a science and math building to Catholic High School for Boys, his alma mater.
[6] On December 28, 2008, John and Denise York announced that their son, Jed York, would become team president and operating head of the franchise, while they would become co-chairpersons responsible for providing resources and maintaining their role of interacting with other owners and NFL executives.
[8] On May 24, 2018, the York family via 49ers Enterprises (the 49ers' business arm) bought shares in English soccer club Leeds United to become a minority investor.