The regiment was constituted on July 28, 1866 in the Regular Army as the 7th Cavalry. It was organized on September 21, 1866 at Fort Riley, Kansas as part of an expansion of the Regular Army following the demobilization of the wartime volunteer and draft forces. From 1866 through 1871, the regiment was posted at Ft. Riley and fought in the Indian Wars, notably at the Battle of the Washita in 1868.
Typical of post-Civil War cavalry regiments, the Seventh was organized as a twelve company regiment without formal battalion organization. However, battalions — renamed "squadrons" in 1883 — did exist. Companies A–D were assigned to 1st Battalion; Companies E–H were assigned to 2nd Battalion; and Companies I–L were assigned to 3rd Battalion. Throughout this period, the cavalryman was armed with Colt Single Action Army .45 caliber revolvers and single shot Springfield carbines, caliber .50–70 until 1870 and caliber .45–70 until 1892. He used one of the many variants of the McClellan saddle. Sabres were issued but not carried on campaign.
From 1871 through 1873, 7th Cavalry companies participated in constabulary duties in the Reconstruction South, and again in 1874-1876 for half the regiment. In 1873 the 7th Cavalry moved its garrison post to Fort Abraham Lincoln, Dakota Territory. From here, the regiment carried out the historic reconnaissance of the Black Hills in 1874, making the discovery of gold in the Black Hills public and starting a gold rush that precipitated the Black Hills War. Lieutenant Colonel George A. Custer's disaster at the Battle of the Little Bighorn on June 25 and 26, 1876, while a stunning defeat, demonstrated the sheer bravery of the 7th Cavalrymen: fourteen soldiers received the Medal of Honor during that battle. The regiment was present at the Wounded Knee Massacre on December 29, 1890, the end of the Indian Wars.
From 1895 until 1899, the Regiment served in New Mexico (Fort Bayard) and Oklahoma (Ft. Sill), then overseas in Cuba (Camp Columbia) from 1899 to 1902.
An enlisted trooper with the Seventh Cavalry from 1895 to 1897 at Fort Grant Arizona Territory was author Edgar Rice Burroughs.
In 1903 the Army replaced the Krag .30–40 with the M1903 Springfield Rifles, initially in caliber .30–03 and later in its more familiar .30–06 form. In 1911, the Army adopted the superb M1911 Automatic Colt Pistol, replacing the Colt single and double action .45 and .38 caliber revolvers.
The Regiment served in the Philippines during the Philippine-American War from 1904 through 1907, with a second tour from 1911 through 1915. Back in the United States, the Regiment was once again stationed in the southwest, in Arizona (Camp Harvey J. Jones), where it patrolled the U.S.-Mexico border and later was part of the Mexican Punitive Expedition of 1916 to 1917.
In December 1917, 7th Cavalry was assigned to the 15th Cavalry Division, a on-paper organization designed for service in France during World War I that was never more than a simple headquarters because of the speed in which the war ended after the entry of the United States. 7th Cavalry was released from this assignment in May 1918.
On September 13, 1921, 7th Cavalry Regiment was assigned to the 1st Cavalry Division, which assignment was maintained until 1957. The Division and its 2nd Brigade was garrisoned at Fort Bliss, Texas, while the 1st Brigade was garrisoned at Douglas, Arizona. Additional garrison points were used as well.
7th Cavalry Regiment continued to train as a horse cavalry regiment right up to World War II, including participation in several training maneuvers at the Louisiana Maneuver Area on April 26–May 28, 1940; August 12–22, 1940; and August 8–October 4, 1941.
World War II
7th Cavalry Regiment was dismounted on 
