It traced its roots back to the American Revolutionary War, although its official U.S. Army lineage begins in 1881.

Included in the company were: The 115th Infantry has long claimed lineage and honors that have not been recognized by the U.S. Army Center of Military history.

[citation needed] The 115th Infantry claims lineage back to the earliest militia units formed to protect the frontier of western Maryland.

The first two companies to leave Maryland were assembled in Frederick in the summer of 1775 under the command of Captains Cresap and Price; they were organized in response to the Continental Congress' call to active duty.

During this battle, in which the Confederates were successful, Colonel Kenly gave utterance to the famous command, "Rally round the Flag," which is to this day the motto of the 115th Regiment.

On 28 June 1916 the regiment was again called into active service and saw duty at Eagle Pass, Texas during the Mexican Border Incident.

During the Meuse-Argonne offensive they would fight for 21 straight days, moving over 6 miles (9.7 km), throwing back elements of six enemy divisions, and suffering a staggering 4,781 casualties in the process.

The 1st Battalion, 115th Infantry, is authorized two campaign streamers for its service in World War I: one for Alsace and one for Meuse-Argonne.

The 115th Infantry arrived at the port of Newport News on 24 May 1919 on the troopship USS Artemis and was demobilized 7 June 1919 at Camp George G. Meade, Maryland.

It then moved on to Camp Blanding to fill its empty personnel slots on 19 August 1942, and then staged at Camp Kilmer on 20 September 1942, and shipped out from the New York Port of Embarkation on 5 October 1942 on the RMS Queen Mary and RMS Queen Elizabeth.

The main port the Allied forces hoped to seize and put into their service was Brest, in northwestern France.

Brest also served as a major German U-boat base from 18 June 1940 until its surrender to U.S. forces during the Brittany Campaign.

The regiment returned to the New York Port of Embarkation on 16 January 1946, and mustered out at Camp Kilmer the next day.

Campaign streamers for Normandy (with arrowhead), North France, Rhineland, and Central Europe were added to the colors.

In 1968, due to changing requirements, the division's colors were retired and its elements broken up into separate brigades.

In October 2001, in the aftermath of terrorist attacks on the continental United States, the battalions of the 115th were called to active federal service as part of Operation Noble Eagle.

On 6 January 2005, Company B, 1–115th Infantry, mobilized again for active duty as part of Operation Iraqi Freedom.

For the first 5 months they conducted operations in a town called Saba Al boor north of Baghdad that had a population of between 50,000 and 65,000.

B Co 1/115th was the main effort for Task Force 2/70th Armor which is an active duty unit from Ft. Riley, Kansas.

B Co conducted raids, counter IED ambushes, air assaults, cordon and searches as well as combined patrols with the Iraqi Army.

For the remaining 7 months they performed convoy security operations out of the Marine base at Al Asad.