He then went to the University of Chicago where he undertook research under the supervision of Eliakim Moore . Lehmer was awarded his Ph.D. in 1900 from the University of Chicago for his thesis Asymptotic Evaluation of Certain Totient-Sums.
Siya pagkatapos ay nagpunta sa University of Chicago kung saan siya undertook pananaliksik sa ilalim ng pangangasiwa ng Eliakim Moore. Lehmer ay iginawad sa kanyang Ph.D. sa 1900 mula sa University of Chicago para sa kanyang tesis Asymptotic Pagsusuri ng ilang Totient-Sums.