The 28th Infantry Division ("Keystone") is a unit of the Army National Guard and is the oldest division-sized unit in the Department of Defense. Some of the units of the division can trace their lineage to Benjamin Franklin's battalion, The Pennsylvania Associators (1747–1777). The division was officially established in 1879 and was later redesignated as the 28th Division in 1917, after the entry of America into the First World War. It is today part of the Pennsylvania Army National Guard, Maryland Army National Guard, Ohio Army National Guard, and New Jersey Army National Guard.