Fulton County was created from the western half of DeKalb County in 1853.  It is often assumed Fulton County was named for the inventor, Robert Fulton who built a steamboat in 1807 in addition to numerous other inventions.  This assumption is likely because the steam engine was the predecessor to the steam locomotives which built Atlanta.  Some research however indicates it may have been named to honor Hamilton Fulton, a surveyor for the Western and Atlantic Railroad.