Adlai Ewing Stevenson II was born on February 5, 1900 in Los Angeles, California. He was born to a prominent Illinois political family, the grandson of Adlai Stevenson, who served as Vice President under President Grover Cleveland, and Lewis Stevenson, who served as the Illinois Secretary of State from 1914-1917. Stevenson was raised in Bloomington, Illinois. After attending both Bloomington High School and University High School in Normal, Illinois, he graduated from The Choate School in 1918.

Stevenson enlisted in the United States Naval Reserve in 1918 and served as a seaman apprentice while undergoing training. The war ended prior to the completion of his training, and Stevenson was discharged as a seaman second class in January 1919. Stevenson then attended Princeton University, graduating in 1922 with a B.A. in literature and history. He attended Harvard Law School but withdrew after failing several classes, after which he returned to Bloomington to write for the family’s newspaper, The Daily Pentagraph. Stevenson returned to law school a year later, now attending Northwestern University School of Law, and received his J.D. degree in 1926 and passed the Illinois state bar examination the same year. He joined Cutting, Moore, and Sidley, a prestigious law firm in Chicago.

From 1940 to 1944, Stevenson worked as Principal Attorney and special assistant to Major Frank Knox, then Secretary of the Navy. He worked in various roles with the State Department between 1945 and 1947, and in 1948 won the Illinois gubernatorial race against the Republican incumbent Dwight H. Green.

Stevenson ran unsuccessfully for president in 1952 and 1956, losing both times to Dwight D. Eisenhower. He resumed law practice in 1957, forming law firms based in Washington, D.C. and Chicago, Illinois with Judge Simon H. Rifkind. After a failed bid at the 1960 nomination, Stevenson campaigned on behalf of Kennedy despite strained relations between the two. Kennedy appointed Stevenson as the U.S. Ambassador to the United Nations in 1961, and he held the position until his death on July 14, 1965.