Greenwood's career includes serving as Senior Vice President of American Express and a member of the boards of directors of American Express Publishing Company and other subsidiaries of the worldwide corporation. He has held senior executive positions in over "Fortune 500" companies and in President Ford's Administration. He has been Chairman of Children On The Go, Inc. and Career Counsellors, Inc. He has also served as member of the boards of directors of a bank holding company, a chain of supermarkets and an advertising and public relations agency.