John James Mortensen, Jr.

John James Mortensen Jr., affectionately known as Jack, passed away peacefully on April 23, 2025, at the age of 83, surrounded by his loving family in Jacksonville, Florida, following an extended illness.

Born on May 31, 1941, in New York City, Jack lived a life defined by dedication, curiosity, and love. He earned a degree in geology from Columbia University, nurturing a lifelong fascination with the natural world. He proudly served in the United States Navy for 20 years, retiring with the rank of Lieutenant Commander. During his service, Jack was stationed in several places around the world, including Spain, Naples, Italy, and Jacksonville, Florida. He served in Vietnam as a Naval Supply Officer, where he was well known for his culinary skills, often concocting creative recipes for the troops with limited ingredients. His ability to turn simple supplies into meals that brought comfort and morale to his fellow servicemen was one of his many talents.

After retiring from the Navy, Jack worked for Grumman in St. Augustine, rebuilding fighter jets. His final job was managing a pet store in Orange Park, where he could share his deep love for animals. Jack was an avid pet enthusiast and cherished every opportunity to care for and connect with animals.

In addition to his work, Jack loved the outdoors — especially fishing, camping, and enjoying nature. He was a lifelong subscriber to National Geographic and an avid reader, known as a “walking encyclopedia.” Jack had a photographic memory and seemed to remember everything he ever read, which made his stories rich with detail and his conversations endlessly fascinating. His love for classical music filled his home, and he took great joy in sharing stories and knowledge with those around him.

Jack’s greatest joy, however, was his family. He worked hard to ensure his children had a childhood filled with adventure, exploration, and lasting memories. Whether camping under the stars, planning spontaneous day trips, or simply encouraging curiosity about the world, Jack created a home where love, learning, and togetherness were at the heart of everyday life. One of his most treasured traditions was tent camping in a secret spot in St. Augustine, Florida, a place where the family has vacationed since his children were young. This tradition continues today, with Jack’s children and grandchildren carrying on the legacy of these special family moments.

Jack was preceded in death by his beloved wife Irene, his father John Sr., mother Margaret, and sisters Joan and Margie. He is survived by his son John, daughters Kathy, Kristen, and Kim; grandchildren Kaiden and Amora; niece Nancy; and nephews Steven and Peter. Jack connected with his daughter Kim later in life, and their bond brought a new sense of joy and reflection to his final years.

Jack was deeply loved and will be profoundly missed by all who had the privilege of knowing him. His legacy endures in the stories he told, the wisdom he shared, the boundless love he gave so generously, and the unforgettable sayings he left behind—quirky expressions and humorous memories that continue to bring smiles and comfort to his family every day.

A private service to commemorate Jack’s life will be held this summer at Jacksonville National Cemetery, a U.S. Department of Veterans Affairs cemetery. Date to be determined.