This is a list of historical formations of the United States Army. Units still in existence are in bold. For specific eras: * Formations of the United States Army during the Mexican Revolution * Formations of the United States Army during World War I * Formations of the United States Army during World War II * Formations of the United States Army during the Vietnam War * Formations of the United States Army during the War on Terrorism * Formations of the United States Army (current)