Mary C. Gerhartz (née Koch) passed away on Oct 12, 2017. She was 100 years young.   Mary was born on August 4th, 1917 in Portage, WI. to Charles and Emelia (Eberlein) Koch. Mary was a graduate of Portage High School, Julia Rusch was her teacher/principal.    She married Merlin Gerhartz.  As a civilian worker she assisted the World War II effort, following her husband to war.  Mary worked for City Bank of Portage, and Leahy Motor Sales.  She retired in 1979.  Mary was a member of Trinity United Church of Christ. She was an accomplished pianist.   Mary was the mother she didn't have to be.  She adopted Bob at 2 years of age and has loved him as her own. Mary is survived by her son Robert, Portage.  Grandchildren Michael Gerhartz, Baraboo, Rebecca Tierney, Patrick Gerhartz, Portage, Amy Kennedy (Rory) of Markesan, and their mother Christy Bahr.   Twelve great grandchildren, Alexander, Gavin, Benjamin and Elizabeth Gerhartz, Thomas, Henry and Kegan Tierney, Brody, Marin, Judie, Veira, and Alice Kennedy.  A niece Deena Holstein of Marengo, IL.    She was preceded in death by her husband, Merlin, her parents, her brothers Walter and Fredrick Koch. Mary will be inurned in a family ceremony at Silver Lake Cemetery.    There will be a celebration of life for Mary C. Gerhartz, on Sunday Oct. 29th, at 1 P.M..    Trinity UCC, 503 Prospect Ave.,  Portage. The family would like to thank CHCC Wyocena, for the excellent care she was given.  A special thanks to Debbie, Irene, mother's pal "Charlie". Service Details. Visitation