After having worked his way up from assistant cashier in the Bank of Odell (Illinois) to its presidency, he moved to Pasadena, where he and his wife Carolyn had three children, Julia, John III, and Dorothy. On the West Coast, McWilliams continued as a banker and expanded his interests to include a conglomerate of Arkansas farms, became involved in real estate, and served as president of the Pasadena Chamber of Commerce. In addition he served as a director or trustee for numerous businesses and charitable organizations. McWilliams’ devotion to Princeton was notable as well. His Princeton Alumni Weekly obituary (February 23, 1965) notes that he served as a regional trustee, an alumni association representative for Los Angeles, vice president of his class, member of the Class of 1901 Executive Committee, and former president and vice president of the Princeton Club of California. He also founded the John McWilliams Scholarship in memory of his father and donated carrels for Firestone Library.