Group Health was officially registered as a corporation in Washington on December 22, 1945. Group Health's founders included Thomas G. Bevan, then president of lodge 751 of the International Association of Machinists and Aerospace Workers at Boeing; Ella Willams, a leader in a local chapter of The National Grange of the Order of Patrons of Husbandry; Addison Shoudy, R.M Mitchell, and Stanley Erickson, who were pioneers in the American cooperative movement; and other community members who had no strong past affiliation with any particular social group.