SAN MARCOS, Calif. — Dan Sullivan, a retired telecommunications executive who led development of worldwide banking networks, and maintained lifelong interests in music, flying and travel, died Wednesday, July 27. He was 71.

Born in 1940 in Lewiston, he grew up in Auburn, where his parents, Alexander Sullivan and Blanche Cassista Sullivan, ran a corner grocery store. He graduated as valedictorian from St. Dominic High School.

He earned a Bachelor of Science in Electrical Engineering at Notre Dame University, where he served in the Naval ROTC and played saxophone in the Notre Dame marching band and clarinet in the university’s concert band. While the band labored over complex arrangements, he said it was the Notre Dame Fight Song that roused crowds. He also earned a Master’s in Engineering from Northwestern University and a PhD in Engineering from Notre Dame.

Dan met his college sweetheart Jeanette at a sock hop at Notre Dame. They married in Chicago on New Year’s Eve, 1965, and had three children.

He worked as an Assistant Professor of Engineering at the University of Missouri, then as a researcher at Bell Labs in New Jersey.

In 1974, Citibank recruited him to lead development of the first ATM network. Later, as a Vice President for the company, he worked in Los Angeles and New York as chief architect for Citibank’s global networks, said former Citicorp Vice President Malcolm Hamer.

“He was very popular and well liked, and everybody would defer to him because he was knowledgeable and a consensus-builder,” Hamer said.

With a gentle disposition and wry sense of humor, Dan joked that engineering was a fallback career. His dream job, he said, would have been that of symphony conductor or airline pilot.

Dan retired from Citicorp in 1998, teaching Communications Theory at Columbia University in New York before moving to Carlsbad, Calif. He also taught at U.C. San Diego.

Throughout his life, he delighted in travel and cultural exploration.

Pursuing a love of classical music, he took music appreciation classes at the Juilliard School, and joined an Elderhostel tour of Europe to attend world renowned symphonies and study composers including Mozart, Beethoven and his favorite, Gustav Mahler.

A recreational sailor and instrument-rated private pilot, he flew from New York to the Bahamas with his wife Jeanette for their dream vacation. Dan and Jeanette also journeyed to Egypt, Greece, Tahiti, Argentina and the Galapagos Islands, and toured Lewis and Clark’s trail in 2005 for the 200th anniversary of the expedition.

A lifelong Red Sox fan and Notre Dame football follower, Dan loved watching baseball at Fenway Park and visiting Notre Dame for alumni games.

As a father, he quietly nurtured his children’s sense of intellectual curiosity and accomplishment, Dan’s son David Sullivan said.

“He was soft-spoken, which made his words more powerful,” he said. “It was pretty easy to make him happy and proud, but that just made you try harder.”

As Dan struggled with Parkinson’s disease in later years, he joined “The Tremble Clefs,” a therapeutic singing group for people with Parkinson’s, performing popular standards and solos including “Danny Boy,” “The Thing” and “Galway Bay.”

He died of melanoma July 27, and is survived by his wife, Jeanette; daughter, Deborah Sullivan Brennan (Kevin Brennan); and sons David Sullivan (Natasha Rado) and Lawrence Sullivan (Elizabeth Sullivan); grandchildren, Malachy and Ailish Brennan, and Kendall Sullivan; sister, Claire Kubasik; and numerous nieces, nephews and cousins in California, Illinois and New England.

Years before his death, Dan stated his own epithet; “I had a wonderful life. God was good to me. I had more than my share of happiness.”