Jay W. Forrester died peacefully at home in Newbury Court, Concord, MA on November 16, 2016 at the age of 98. He was born July 14, 1918 on a cattle ranch 18 miles west of Anselmo, Nebraska that was homesteaded by his father, Marmaduke Montrose Forrester, and his mother Ethel Wright Forrester. Jay went to a one-room country school and developed an early interest in electricity. As a teenager he assembled a wind turbine from old auto parts which, along with batteries in the storm cave, brought electric light to the ranch house for the first time. He attended high school in Anselmo and then graduated from the University of Nebraska in Lincoln with a degree in electrical engineering. Jay moved east in 1939 to study at MIT where he earned a Master's degree in electrical engineering. During World War II he worked at the MIT Servomechanisms Lab on ship-born radar stabilization devices, serving briefly as a civilian on the carrier Lexington. After the war he lead MIT's Project Whirlwind that developed one of the first high-speed digital computers. As part of the Whirlwind effort he invented and patented random-access magnetic core memory, the dominant form of computer RAM until the advent of semiconductors in the 1970s. Next he directed Division 6 of MIT's Lincoln Laboratory during the development of the SAGE air defense system. In 1954 Jay joined the Sloan School of Management where he taught and lead research until his retirement in 1989. During his tenure at the Sloan School he developed a new field called system dynamics involving computer modeling of complex business, social, and economic systems. His students came from all over the world and spread the approach world-wide. He published several books and numerous articles. Key works include Industrial Dynamics (1961), Urban Dynamics (1968), and World Dynamics (1970). His group worked for several years modeling the US economy and including causal roots of very long cycles (Kondratieff waves) of boom and depression. System dynamics has been used by firms in many industries to enhance growth, deal with cycles, and as a tool in litigation. Jay married Susan Swett, who grew up in Southern Pines, NC in 1946 and they were married some 64 years before she passed away in 2010. They moved to Concord in 1952 where they raised their children. They leave three children, Judith of Concord, MA, Nathan of Boca Grande, FL, Ned of Falmouth, MA, four grandchildren, Matthew Forrester of Arcadia, CA, Julia Forrester of Boise, ID, Neil Forrester of Torrance, CA, and Katherine Forrester of Chicago, IL. and two great-grandchildren, Everett Chen Forrester and Faraday Chen Forrester, both of Arcadia, CA. A memorial service will be held at Trinity Episcopal Church, 81 Elm St., Concord, MA on Saturday, December 10th at 10 am. Burial will take place at a later date in a family plot in North Carolina. Arrangements are under the care of the Dee Funeral Home of Concord.