[2] Thompson left Harrisburg to attend law school in Chicago.

He graduated from the Chicago-Kent College of Law (1918) and was admitted to the Illinois Bar in 1919.

[4] In 1926, he was elected as a Republican to represent the 51st district in the Illinois State Senate.

[2] From 1936 to 1937, he served as president of the Federation of Local Bar Associations chapter for Illinois' first supreme judicial district.

[4][5] In 1942, Thompson won election to a first district seat on the Supreme Court of Illinois.

[2] After retiring from the court, Thompson returned to practicing law in Harrisburg.