Dennis was born August 16, 1930 at Holy Cross Hospital on the South Side of Chicago IL and passed away March 23, 2025 at 94.

Dennis was the eldest son in a family of five, with three sisters and one younger brother to keep him in check. The family grew up in Cecil Wisconsin where he spent his younger days fishing for Walleye in Shawano Lake or making a dollar by pulling tassels off the cornstalks at one of the local farms. He purchased his first car there, a Ford Model T, which started his lifelong love of cars.  He graduated from Shawano High School in 1948 and from 1948-1950 attended St. Norbert College in Wisconsin, where he balanced his pursuit of the outdoor recreation with an intellectual curiosity that would direct his future. It's unknown whether the newly built Shawano Municipal Airport influenced him – but he graduated from University of Detroit in 1953 with a BS in Chemical Engineering where he developed an interest in aeronautics and the growing air travel industry.

Legend has it that shortly before graduation Dennis and a friend went to a job fair. He submitted multiple applications, but Boeing was the only company that offered him, as well as his friend, a job. He lost a bet with the friend and ended up riding a motorcycle out to PNW to begin his career with Boeing.  He worked in the Materials and Technology division, specializing in plastics and adhesive materials. His dedication and knowledge earned him a patent in 1977 for a process that facilitated the protection and bonding of aluminum. It was also in Seattle that he met his first wife Suzanne.  They enjoyed skiing and many outdoors adventures in the area.  Quickly enough, 8 kids came along, and Dennis continued his outdoor adventures camping, salmon fishing and hunting, often with a few kids in tow. Over the years, Dennis pursued many other interests including building a 17-foot sailboat by hand, tinkering on cars and boats, and playing both tennis and golf. He had a passion for electronics, and he bought the DIY "Heathkits" to build the family's first stereo and television set.  The older kids helped sort the resistors and chips and watched in fascination as he soldered them together.  The resulting units lasted forever. He was an early personal computer enthusiast and brought home one of the first ATARI game systems.  This love of electronics lasted his lifetime.   He even bought himself a smart watch just a few weeks before he passed.

Dennis retired after a long and fulfilling 39 year career from The Boeing Company.  He was able to move around in Boeing during that time and worked on many exciting and different projects including the Lunar Land Rover.  He was excited to move on to the next chapter in his life and run around with his grandchildren.

Later, making good use of his computer skills, he was a pioneer in online dating, where he met his second wife Margie. Margie was a welcomed addition to the family and changed him for the better. The two of them made the most of every opportunity, keeping each other young at heart along the way.

After his retirement, Dennis was able to fully enjoy his lifelong love of fishing and golf, and while he was never one to brag, he regularly won the bounty for most fish caught. His ability to think his way around the golf course often netted him a few dollars in his Boeing Retirees league. He was skilled without being showy, he had excellent body balance to match his quiet yet strong mental determination.  Almost unbelievably, he was able to 'shoot his age' on a Golf Course, shooting 90 on his 90th birthday. Just to show that it wasn't a fluke – he did it again on his 91st.  Dennis was also a long-time member of the Boeing Employees Tennis Club. He was still playing in the leagues at age 93 and was awarded the "2024 Iron Man Award".

Dennis is survived by his wife Margaret, sister Barbara Schneider of Cecil, WI, brother Michael Donnelly (Carmel) of Surprise, AZ, children Kathleen (Casey) Erickson (Kevin), Michaela Gould (Brad), Maureen Krueger, Patrick Donnelly, Matthew Donnelly (Suying), Thomas Donnelly, Sheilagh Heiges (Jay), Sean Donnelly and numerous Grand and Great-Grandchildren.  At his request, there will be a private family service.

In lieu of flowers, memorials may be sent to the WA Department of Fish and Wildlife or Catholic Community Services.