[5] He was instrumental in solving complex social and ethical issues during the era of discrimination and segregation in the United States.

While in China, he met a fellow medical doctor named Helen Vincent whom he married in 1923.

[7] In 1916 the Rockefeller Foundation sponsored his trips to China to found the Peking Union Medical College.

He was appointed Director of the college,[8] but did not stay for any length of time until 1920 due to his active army duty during World War I.

In 1923 McLean was invited to direct the new medical school envisioned by the University of Chicago and set forth planning, overseeing and raising the funds necessary.

In 1929 he resigned the department chair so as to assume the title of Director of University Clinics and Assistant to the President in Medical Affairs.