John Brooks entered the university in 1859 and left the institution early in 1861 to join the Confederate army. While a student, he organized the first two military companies and was the first instructor of military tactics and commandant. He was a member of the Chi Delta Literary Society.
At the Battle of Chickamauga, he was so seriously wounded that the army physician ordered his grave dug, but Brooks recovered completely after a 12-month stay in the hospital. He surrendered near Charlotte, North Carolina, in the spring of 1865. Following the war, he returned briefly to Knoxville and then went to Bristol. Two years later, he returned to Knoxville and entered the drug business under the name of McClanahan & Brooks. After two successful years, the firm was burned out. He then connected himself with W. C. Ingles & Co., and that firm was also burned out. He then went into the fire insurance business.
In 1889 he went to Kentucky and took charge of the Middlesboro Town Company, a real estate organization promoted with English capital. For six years, he was president of the company. He founded the city of Middlesboro, secured its charter, and was its first mayor. He returned to Knoxville in 1902 and entered the insurance business. He was elected mayor of Knoxville in 1908 and served one term.