The rank of brigadier general has existed in the U.S. military since the inception of the Continental Army in June 1775. To prevent mistakes in recognizing officers, a general order was issued on July 14, 1775, establishing that brigadier generals would wear a ribband, worn across the breast, between coat and waistcoat, pink in color. Later, on June 18, 1780, it was prescribed that brigadier generals would instead wear a single silver star on each epaulette. At first, brigadier generals were infantry officers who commanded a brigade; however, over the course of the 19th and 20th centuries, the responsibilities of the rank expanded significantly.
During the period from March 16, 1802, to January 11, 1812, the rank of major general was abolished and brigadier general became the highest rank in the U.S. Army. Foreseeing the need for an expanded general staff in case of war, which seemed imminent, Congress restored the rank of major general in January 1812.
The first brigadier general in the U.S. Marine Corps was Commandant Archibald Henderson, brevetted to the rank of brigadier general in the 1830s for his service in the Second Seminole War. The first non-brevet brigadier general in the Marines was Commandant Jacob Zeilin who was promoted to the rank in 1874, but when he retired in 1876, colonel once again became the highest rank in the Marines until March 1899 when Commandant Charles Heywood was promoted. Ever since then, the office of Commandant has been held by a general officer, with the permanent rank of the commandant raised to major general in 1908, and then to lieutenant general and subsequently to general during World War II, which rank it has held ever since.
The insignia for a brigadier general is one silver star worn on the shoulder or collar, and has not changed since the creation of the rank two centuries ago. Since the Mexican-American War, however, the lower rank of colonel has been the normal rank appointed to command a brigade that is organic to a division (e.g., the 1st Brigade of the 94th Infantry Division, vice the 187th Infantry Brigade).
Today, an Army or Marine Corps "BG" or "BGen," respectively, typically serves as deputy commander to the commanding general of a division or division-sized units and assists in overseeing the planning and coordination of a mission. In an Army infantry brigade not organic to a division, a brigadier general serves as the unit's commander, while a colonel serves as deputy commander. A Marine Expeditionary Brigade (MEB), as the medium capability (and sized) scalable Marine Air Ground Task Force (MAGTF) with up to 20,000 Marines, is normally commanded by a Marine BGen. An Air Force brigadier general typically commands a large wing or serves as the deputy commander for a NAF. Additionally, one-star officers of all services may serve as high-level staff officers in large military organizations.