Johnson was born in Philadelphia, Pennsylvania, USA, on 1 May 1894. He claimed to be a grandson of U.S. President Andrew Johnson. His father, James Edward Johnson, the manager of the Baltimore and Ohio Railway station in Philadelphia, was alleged to be the illegitimate love-child of the former President.
In 1917, he was drafted into the United States Army and served in the Fourteenth Company, 154th Battalion. Johnson did not see combat during the war, but served at Fort Greene, North Carolina and Fort Dix, New Jersey.
After his discharge in 1919, Johnson got married to his high school sweetheart Ida Dulany, and moved to California. In 1927, Johnson and his wife opened a restaurant, although it failed after less than a year.
In April 1930, the couple moved to San Francisco, and later to Richmond, California in 1938. They never had children.
When asked about the secret of his longevity, he attributed it to clean living free from drugs, alcohol, and tobacco. On his 112th birthday, he was unable to see.
Johnson died in Richmond, California, USA, on 30 August 2006, at the age of 112 years, 121 days.
His age was verified by L. Stephen Coles and Robert Young, and validated by the GRG on 25 September 2004. Coles visited him in June 2006.
Following the death of the 112-year-old Marion Higgins of Seal Beach on 2 March 2006, it was believed that George Johnson had become the oldest known living Californian – a distinction he held until his own death at the age of 112 years, 121 days. However, a woman about one month older, Gertrude Baines, was validated not long after he died, so George lost this status posthumously.