Shanks was born in 1898, and left Fairmont in 1912 at the age of fourteen. His father was the pioneer Fairmont Postmaster, Edgar Shanks, and he lived at 304 Woodland Avenue. He attended the University of Washington, graduating in 1921. He then attended law school at Columbia University, graduating in 1925. After law school, Shanks joined the law firm of Root, Clark, Buckner, and Ballantine in New York City. He was with the firm from 1925-1929, and also lectured at Columbia Law School during that time. He then became an associate professor at Yale, and later returned to his former law firm in 1931. In 1932, Shanks joined the Prudential Life Insurance Company of America. He became a vice president in 1944, advanced to executive vice president and director, and eventually became president of the company in 1946.