Born near Petersburg, Virginia, Cobb attended the common schools.

He joined a volunteer company from his native county in 1861 and served throughout the Civil War in the Army of Northern Virginia.

After the war, he moved to St. Louis, Missouri in 1867 and was employed as a clerk in a grain commission house.

He was not a candidate for renomination in 1896, and he resumed the grain commission business in St. Louis.

In 1904, he served as vice president of the Louisiana Purchase Exposition at St. Louis.