[4][5] Nolan began his career with the Chicago Police Department in 1945, serving as a foot patrol officer for three years before spending a decade as a robbery detective.

[2] In 1962, then-superintendent Orlando Wilson appointed Nolan the head of the police department's human relations unit, established to deal with "racial, religious, or nationalistic incidents".

[2] In 1965, Nolan took a leave of absence from the police department to serve as deputy director of the Chicago Commission on Human Relations.

[7] In 1977, after the Humboldt Park riot, then-mayor Michael Blandic appointed Nolan and deputy commissioner Hugh Osborne and to represent the city in meetings with Latino community groups.

[8] In July 1979, mayor Jane Byrne created the position of public safety commissioner, naming Nolan its inaugural appointee.