John Dennis Lanigan

Dennis Lanigan passed away peacefully in Colorado Springs, CO, on May 31, 2025, at age 88. He was born August 25, 1936, in Shanghai, China, to Ann White and Brigadier General John Ralph “Pat” Lanigan, USMC. As the son of a Marine Corps officer, Dennis spent his early years living in an array of places, including: Philadelphia, PA; Washington, D.C.; Camp LeJeune, NC; Clearwater Beach, FL; Arlington, TX; Guantanamo Bay, Cuba; Parris Island, SC; and Dade City, FL. At age 16, with special permission from the Secretary of the Navy, he enlisted in the Marine Corps Reserve, becoming the youngest person ever to do so. That same year he graduated from St. John’s College High School in Washington, D.C., and later attended Sullivan’s Prep School and Georgetown University before entering the U.S. Naval Academy in 1954.

Dennis served with honor in the United States Marine Corps. His first tour was in a reconnaissance company with the 1st Marine Brigade in Kaneohe Bay, HI. He later served as an instructor and company commander at Officer Candidates School in Quantico, VA, and as Commanding Officer of the Marine Detachment aboard the USS Hunley off Dunoon, Scotland. After earning an MS in Operations Research from the Naval Postgraduate School in Monterey, CA, he served briefly at Headquarters Marine Corps before a thirteen-month deployment to Vietnam, where he earned the Legion of Merit for exemplary service. He returned to Headquarters and remained there until his military retirement in 1973, after an unfortunate run-in with a lawn mower resulted in the loss of a few toes, a tale he often told with his trademark wit.

After medically retiring from the Marine Corps, Dennis worked for eleven years as a Principal Scientist with General Research, and then for fifteen years as a computer systems engineer with the MITRE Corporation in McLean, VA; Heidelberg, Germany; and Colorado Springs, CO. He retired in 1999 and spent his later years traveling, playing bridge, supporting the Colorado Opera Festival and the Pikes Peak Opera League, and enjoying the fellowship of The Argonauts, where he once served as President. He was a lifetime member of the Naval Academy Alumni Association and the Military Officers Association of America (MOAA).

What truly defined Dennis was not just his impressive accomplishments, but the way he made people feel. He had a quick wit and a magnetic sense of humor that lit up any room he entered. His smile and laugh were unforgettable, warm, genuine, and contagious. He welcomed everyone with open arms and had an effortless way of making people feel seen and valued. He was deeply loyal, remarkably thoughtful, loving, and always ready to help. Dennis approached life with sincerity, integrity, and optimism, always choosing to see the best in people. His kindness left a lasting imprint on everyone lucky enough to cross his path.

He is survived by his beloved wife of 48 years, the former Karol Isabel Loos of Carlisle, PA; son Brian Lanigan and his husband Eddie, daughters Patricia Jerrell, Kathy Nickles and her husband Brian, Colleen Clark and her husband John, and Andrea Kirshner and her husband Rand; stepson William Hooke and his wife Kristin, stepdaughter Kathleen Hooke and her husband Paul, 22 grandchildren and 22 great-grandchildren, and his brother Kevin Lanigan. He was predeceased by his brother Pat Lanigan and his wife Kathy (Karol’s sister), his brother Michael Lanigan, his stepdaughter Mary Kate Joslin, and his grandson Christopher Mumma.

The family expresses their gratitude to the many Home Instead and Gentiva Hospice caregivers who cared for Dennis with love, compassion and joy.

Contributions may be made in Dennis’ memory to Westside Cares, 2808 W. Colorado Ave., Colorado Springs, CO 80904, a non-profit organization that helps neighbors in need.