McKinsey & Company has been provided strategic advice to corporations and other organizations since 1926, when James O. McKinsey, a University of Chicago professor, opened a consulting office in Chicago. Marvin Bower joined the firm in 1933 and became the firm’s head after McKinsey left to become chief of Marshall Field & Co. Bower established the firm’s core principles and created the practice of management consulting. McKinsey opened its first international office in London in 1959, and has expanded steadily since. It now has over 100 offices in over 50 countries, making it the biggest pure consulting firm in the world.