The 1st Infantry Regiment is a regiment of the United States Army that draws its lineage from a line of post American Revolutionary War units and is decorated with thirty-nine campaign streamers. The 1st Battalion, 1st Infantry is assigned as support to the United States Military Academy at West Point, New York and to furnish the enlisted garrison for the academy and the Stewart Army Subpost. 2nd Battalion, 1st Infantry Regiment is an infantry component serving with the 2nd Stryker Brigade, 2nd Infantry Division at Joint Base Lewis–McChord, Washington.

On 3 March 1791, Congress added to the Army "The Second Regiment of Infantry" from which today's First Infantry draws its heritage. In September of that year, elements of it and the original 1st Infantry Regiment (today's 3rd United States Infantry Regiment (The Old Guard)), with sizable militia complements, all under the command of General Arthur St. Clair, were sent to the Northwest Indian War of the Ohio country. St. Clair served as a major general in the Continental Army and was now appointed "General in Chief," superseding the first commander of the regiment, Josiah Harmar. Fighting against the Miamis, St. Clair's soldiers were untrained, ill-equipped, underfed, and sickly. This resulted in a disastrous defeat in which the entire U.S. Army suffered a loss of about 700 killed and some 300 wounded out of a total strength of around 1,700, with some 100 civilians killed and 50 wounded as well.

In 1792, Congress reorganized the United States Army into the Legion of the United States, a single formation of infantry, cavalry and artillery units under the command of Major-General Anthony Wayne. The 2nd Infantry Regiment was redesignated as the 2nd Sub-Legion, and participated in the decisive victory over the Northwestern Confederacy at the battle of Fallen Timbers on 20 August 1794. In 1796, the Legion of the United States was organized back into the United States Army, and the 2nd Sub-Legion reverted to being the 2nd Infantry Regiment. During the War of 1812, the 2nd Infantry Regiment as well as the 7th and 44th Infantry Regiments, fought in the Battle of New Orleans under General Andrew Jackson. This gives the regiment campaign credit for the War of 1812.

The 2nd Infantry was consolidated May–October 1815 with the 3rd and 7th Infantry (both constituted 12 April 1808), and 44th Infantry (constituted 29 January 1813) to form the 1st Infantry Regiment. In the ensuing years the regiment was primarily concerned with Indian conflicts and the 1st was involved in the Black Hawk War of 1832 and the Second Seminole War from 1839 to 1842. During this time the regiment was commanded by many, now famous commanders including, Colonel Zachary Taylor, who would later become the 12th President of the United States and Second Lieutenant Jefferson Davis, who would become the President of the Confederate States in the American Civil War.

When War broke out with Mexico in 1846, the 1st Infantry Regiment was sent across the border with General Zachary Taylor's Army and participated in the storming of Monterrey where the regiment fought house to house in savage hand-to-hand combat. From Monterrey, the regiment was transferred to General Winfield Scott's command and participated in the first modern amphibious landing in American history at Vera Cruz in 1847.

Following the Mexican–American War, the regiment campaigned in the Texas area against the Comanches until the outbreak of the Civil War in 1861.

After escaping from rebel forces in Texas the regiment returned to the Mid-west and fought in the Mississippi area of operations. The regiment fought in one of the first battles of the Civil War at Wilson's Creek, Missouri, in August 1861. The 1st Infantry then campaigned with General Grant against Vicksburg in 1863. The end of the war found the regiment occupying New Orleans, Louisiana.

After the Civil War the regiment was sent West to fight the Indians once again. The 1st Infantry was consolidated in April 1869 with the 43d Infantry Regiment, Veteran Reserve Corps (constituted 21 September 1865) and consolidated unit designated as the 1st Infantry Regiment. 1st Infantry Regiment campaigned against the Sioux in the 1870s and 1890s and against the Apache, led by Geronimo, from 1882 to 1886.