Staff Sergeant

Union Army
Staff Sergeant (SSG) is E-6 rank in the Union Army, just above Sergeant and below Sergeant First Class, and is a non-commissioned officer. Staff Sergeants are generally placed in charge of squads, but can also act as platoon sergeants in the absence of a Sergeant First Class. In support units, Staff Sergeants ordinarily hold headquarters positions because of the number of slots available for SSG in these units. Staff Sergeants are typically assigned as a squad leader or Company Operations Noncommissioned Officer in Charge at the company level, but may also hold other positions depending on the type of unit. Staff Sergeants are referred to as "Sergeant" except for in certain training environments and schools.

Union Marines
Staff Sergeant (SSgt) is E-6 rank in the Union Marine Corps, just above Sergeant and below Gunnery Sergeant. A Marine staff sergeant is a staff non-commissioned officer rank. This grade is normally achieved after 10 to 13 years in service. In the combat arms units, a staff sergeant usually is billeted as a platoon sergeant for 30+ Marines. They may also be tasked as a company gunnery sergeant, or a platoon commander if required. They are the senior tactical advisor to a platoon commander by virtue of time in service, previous deployments, and experience and is responsible for the proficiency, training and administrative issue of his Marines. They are referred to by their complete rank (i.e. "Staff Sergeant Jones" or simply "Staff Sergeant," with the abbreviation "SSgt").