Mark Edward Connelly passed away at home on Sunday, October 15, 2017, almost exactly a year after the passing of his beloved wife, Betsy. Mark was born in Concord, NH on February 26, 1925 to Mildred (Harp) and James Connelly. He grew up in Kingston, NY, where he was Valedictorian of the Class of 1942. After one year at M.I.T, he joined the Marines, and served from 1943 to 1945. He then returned to M.I.T. and completed his B.S. in Electrical Engineering. It was while working on his M.S. in Physics at Brown University that Mark met Helen Elizabeth Cooke. They married on March 15, 1952 in Pawtucket, R.I. The family (with son, Todd, and twins, Robin & Sarah) moved to the Conantum neighborhood of Concord, MA in 1957. They were joined by youngest son, Scott, in 1960. Mark had a long career as a researcher at M.I.T., starting with work at the Servomechanisms Laboratory, and including projects on hybrid computing, air defense, aircraft simulation, air traffic control, and mass transit. He also advised graduate students on their research. Mark was a huge advocate of mass transit. Along with many other Conantumites, he took the train into Boston every day, and walked across the Longfellow Bridge from North Station to M.I.T. Mark was one of the original Conantum "tennis bums" who played weekly at the Kalmia Woods tennis courts. He and Betsy also enjoyed sailing and were active members of the Concord Sailfishing Group. Mark was committed to community service and relished his involvement in Great Books, FOPAC, land conservation, town planning, and the Youth Group at the First Parish Church in Concord. He was an avid reader, particularly of books on economics, history and political science, and a daily reader of the New York Times and the Boston Globe, highlighting and clipping relevant passages as he went. Mark enjoyed the camaraderie of the "Old Men's Bridge Club", which met every Monday afternoon for years. Another game that Mark played to the very end was cribbage. Mark was preceded in death by his wife Betsy, son Todd and grandson Tanner. He is survived by his three other children & their spouses: Sarah & Rob Caless, Robin & Larry Walden, Scott & Diana Connelly, and Todd's widow, Lucia Connelly; grandchildren Louis Connelly, Walter Connelly, Daniel & Amanda Caless, Peter & Darcy Caless, Alison Caless, Sarah & Jenna Walden McGowan, Nathaniel & Jenna Walden, Sascha Scheider; and four great-grandchildren, McKenna Connelly, Wesley Caless, Jacob Caless and Everett Walden. The family would like to express deep gratitude to Lynn Van Artsdalen and her crew of caregivers (Audrey, Loise, Ann Grace and Joan) for the extraordinary care they gave to Mark in the last year. Mark was also fortunate to have the Ferraioli family as neighbors, who brightened up his days immeasurably. A memorial service for family and friends will be held on Saturday October 21, 2017 at 2 pm in the Duvall Chapel of the Deaconess Abundant Life Community, 80 Deaconess Road, Concord. Burial will be private. Concord's town flag will fly at half-staff on Saturday October 21st in recognition of Mr. Connelly's service to his country in the U.S. Marine Corps during World War II.