Infantry Branch ( United States ) The Infantry Branch is a branch of the United States Army first established in 1775 . History . Ten companies of riflemen were authorized by a resolution of the Continental Congress on 14 June 1775 . However , the oldest Regular Army infantry regiment , the 3rd Infantry Regiment , was constituted on 3 June 1784 , as the First American Regiment Organization . On 3 March 1791 , Congress added to the Army " The Second Regiment of Infantry Army organized into seven infantry regiments , 1815 Ten one year regiments were authorized by the Act of 11 February 1847 . and after the Mexican American war reduced back to pre war levels . ( Mexican War expansion added eight regiments ( designated 9th – 16th Infantry ) , 1847 , but these were discontinued , ) Civil war expansion to 19 regiments In a major expansion under General Order 92 , War Department , 23 November 1866 , pursuant to an act of 28 July 1866 ( 14 Stat . 332 ) , 2d and 3d battalions of the existing 11th - 19th Infantry Regiments were designated 20th – 37th Infantry Regiments , with four new regiments ( 38th – 41st ) to be composed of black enlisted men , and new 42d - 45th Infantry Regiments for wounded veterans of the Civil War . ( Reduced by consolidation to 25 regiments , under General Order 17 , War Department , 15 March 1869 , with the 24th and 25th constituting the black enlisted force . ) On 2 February 1901 , Congress passed the Army Reorganization Act which authorized five additional regiments ( 26th - 30th ) . The Militia Act of 1903 established the National Guard . In 1916 Congress enacted the National Defense Act and under War Department General Orders Number 22 dated 30 June 1916 that ordered seven new Regiments to be organised ; four in the Continental United States , one in the Philippine Islands ( 31st Infantry Regiment ( United States ) , one in Hawaii ( 32nd Infantry Regiment ( United States ) , and one , the 33rd Infantry , in the Canal Zone . In 1917 a new numbering system was set up 1 – 100 for regular army , 101 – 300 for the national guard , 301 and up for the National Army ( USA ) . 167 national guard units were renumbered from the old state system to the new federal system . However the " 69th , and 71st New York " were able to lobby for their old 19th Century numbers which created doubles of these numbers . A new system , the U . S . Army Combat Arms Regimental System , or CARS , was adopted in 1957 to replace the old regimental system . CARS uses the Army ' s traditional regiments as parent organizations for historical purposes , but the primary building blocks are divisions , and brigade became battalions . Each battalion carries an association with a parent regiment , even though the regimental organization no longer exists . In some brigades several numbered battalions carrying the same regimental association may still serve together , and tend to consider themselves part of the traditional regiment when in fact they are independent battalions serving a brigade , rather than a regimental , headquarters . The CARS was replaced by the U . S . Army Regimental System ( USARS ) in 1981 . There are exceptions to USARS regimental titles , including the Armored Cavalry Regiments and the 75th Ranger Regiment created in 1986 . On 1 October 2005 , the word " regiment " was formally appended to the name of all active and inactive CARS and USARS regiments . So , for example , the 1st Cavalry officially became titled the 1st Cavalry Regiment Branch insignia . Two gold color crossed muskets , vintage 1795 Springfield musket ( Model 1795 Musket ) , 3 / 4 inch in height . Crossed muskets were first introduced into the Army as the insignia of officers and enlisted men of the Infantry on 19 November 1875 ( War Department General Order No . 96 dtd 19 Nov 1875 ) to take effect on or before 1 June 1876 . Numerous attempts in the earlier years were made to keep the insignia current with the ever changing styles of rifles being introduced into the Army . However , in 1924 the branch insignia was standardized by the adoption of crossed muskets and the 1795 model Springfield Arsenal musket was adopted as the standard musket to be used . This was the first official United States shoulder arm , made in a government arsenal , with interchangeable parts , caliber . 69 , flint lock , smooth bore , muzzle loader . The standardized musket now in use was first suggested by Major General Charles S . Farnsworth , U . S . Army , while he was the first Chief of Infantry , in July 1921 , and approved by General Pershing , Chief of Staff , in 1922 . The device adopted in 1922 has been in continual use since 1924 . There have been slight modifications in the size of the insignia over the years ; however , the basic design has remained unchanged . The plaque design has the branch insignia , letters and border in gold . The background is light blue . Personnel assigned to the Infantry branch affiliate with a specific regiment and wear the insignia of the affiliated regiment . There is no standard infantry regimental flag to represent all of the infantry regiments . Each regiment of infantry has its own coat of arms which appears on the breast of a displayed eagle . The background of all the infantry regimental flags is flag blue with yellow fringe . Baby Blue – 65014 cloth ; 67120 yarn ; PMS 5415 . The Infantry has made two complete cycles between white and light blue . During the Revolutionary War , white facings were prescribed for the Infantry . White was the color used for Infantry until 1851 at which time light or Saxony blue was prescribed for the pompon and for the trimming on Infantry horse furniture . In 1857 , the color was prescribed as light or sky blue . In 1886 , the linings of capes and trouser stripes were prescribed to be white . However , in 1902 , the light blue was prescribed again . In 1917 , the cape was still lined with light blue but the Infantry trouser stripes were of white as were the chevrons for enlisted men . The infantry color is light blue ; however , infantry regimental flags and guidons have been National Flag blue since 1835 . White is used as a secondary color on the guidons for letters , numbers , and insignia . 14 June 1775 . The Infantry is the oldest branch in the Army . Ten companies of riflemen were authorized by the Continental Congress Resolve of 14 June 1775 . However , the oldest Regular Army Infantry Regiment , the 3d Infantry , was constituted on 3 June 1784 as the First American Regiment . Current configuration . The United States Army Infantry School is currently at Fort Benning .