He was a master in chancery for the Superior Court of Cook County from 1916 to 1917 and again from 1919 to 1921.

In the interim 1917 to 1919, Sullivan served as a field artillery lieutenant in the United States Army during World War I.

He was elected a Judge of the Circuit Court of Cook County and served from 1921 until his appointment to the federal bench in 1933.

[1] Sullivan received a recess appointment from President Franklin D. Roosevelt on November 8, 1933, to a seat on the United States District Court for the Northern District of Illinois vacated by Judge George E. Q. Johnson.

He was confirmed by the United States Senate on February 20, 1934, and received his commission on March 1, 1934.