Mary Adair

Mary Lynne Adair (née Schwendemann), of O’Fallon, MO, passed away peacefully on Tuesday, June 10, 2025, at the age of 69.

Mary is survived by her loving husband, Dennis Adair; her children, Nathan Adair (Ryan Gibson), Emily Adair (Riley Dickerson), and Katy Adair (Joshua Jett); her brother, Harlan Schwendemann (Colette Schwendemann, surviving); and a host of nieces, nephews, godchildren, and dear friends.

She was preceded in death by her father, Gilbert Schwendeman, and her mother, Ethel Schwendeman. She is also reunited in peace with her beloved siblings: sisters Elizabeth “Betty” Chytla (Joseph Chytla, deceased), Patricia “Patty” Holt (Charlie Holt, deceased), and Margaret “Sis” Hemsath (Norb Hemsath, deceased); and brothers Richard “Dick” Schwendemann (Jane Welch, surviving), John Schwendeman (Brenda Schwendeman, surviving), and Eugene Schwendemann (Gwen Schwendemann, surviving).

Mary devoted her professional life to technology as a Computer Analyst and Programmer with National Information Solutions Cooperative (NISC). She was also a proud member of the 4-H organization in St. Peters.

Her passions included reading mystery novels, writing newspaper columns, playing trivia and games, camping, and traveling when she could. Mary was deeply involved in her children’s education and extracurriculars, serving on the PTA, Band Boosters, and Sports Booster Club. She was a godmother and mentor to many, and a true friend to all who knew her.

Mary was dearly loved and will be greatly missed for her wisdom, wit, and generous heart.

In lieu of flowers, memorial contributions may be made in Mary’s name to the Alzheimer’s Association or the Siteman Cancer Center at Barnes-Jewish West.