In his 20-year career with the State highway Department (1913-1933), Dillman became the only man in Department history to work his way up from the bottom ranks to State highway Commissioner. While Commissioner in 1929-1933, he established a program that put an estimated 100,000 men to work on roads in the depths of the Great Depression. Dillman was a strong and early advocate of earmarking gas and weight tax revenues for highway purposes. Development and beautification of roadsides began during his administration. He became President of Michigan Technological University in 1935 and in the next 21 years guided the development of its top-ranking engineering school, training ground for many hundreds of highway engineers.