Founded in 1922 in Cambridge, Massachusetts, Raytheon grew from a maker of radio power tubes into a major American defense and electronics company. Its breakthrough came in World War II, when mass production of magnetrons helped make advanced radar practical; Percy Spencer’s later work with that technology led to the microwave oven. After the war, Raytheon expanded into guided missiles, radar, and military electronics, with systems such as Patriot helping define its reputation. It also contributed to aerospace and consumer technology, including the Apollo Guidance Computer and household microwaves. In 2020, it merged with United Technologies, ending its separate corporate existence.