From the U.S. Army website:
Modern Day Rangers trace their linage to World War II when Maj. William O. Darby stood up 1st Ranger Battalion June 8, 1942 at Carrickfergus, Northern Ireland. The 3rd and 4th Ranger Battalions were activated and trained by Col. Darby in Africa near the end of the Tunisian Campaign. 2nd and 5th Ranger Battalions participated in the June 6, 1944 D-Day landings at Omaha Beach Normandy. The 6th Ranger Battalion was the first American force to return to the Philippines with the mission of destroying coastal defense guns, radio stations, and other means of defense communications in Leyte Harbor.
The 75th Infantry Regiment (5307th Composite Unit) was the first United States ground combat force to meet the enemy on the Continent of Asia during World War II. It was during the campaigns in the China-Burma-India Theater that it became known as "Merrill's Marauders," after its commander, Major General Frank D. Merrill.
The outbreak of hostilities in Korea, June 1950 again signaled the need for Rangers. The first cycle completed their training November 13, 1950. The 1st, 2nd, and 4th Ranger Companies prepared for overseas shipment. The 3rd Ranger Company prepared to assist in training the second cycle, which consisted of the 5th, 6th, 7th and 8th Ranger Companies. The Rangers went into battle by land, sea or air.
With the growing United States involvement in the Vietnam War, Rangers were again called to serve their country. The 75th Infantry was reorganized once more on January 1, 1969, as a parent regiment under the Combat Arms Regimental System. Fifteen separate Ranger Companies were formed from this reorganization. Thirteen served proudly in Vietnam until inactivation on August 15, 1974.
The outbreak of the 1973 Middle East War prompted the Department of the Army to be concerned about the need for a light mobile force that could be moved quickly to any trouble spot in the world. On January 25, 1974, Headquarters, United States Army Forces Command, published General Orders 127, directing the activation of the 1st Battalion (Ranger), 75th Infantry, with an effective date of January 31, 1974. On July 1, 1974, 1st Battalion (Ranger), 75th Infantry, parachuted into Fort Stewart, Georgia.
2nd Battalion (Ranger), 75th Infantry soon followed with activation on October 1, 1974. These elite units eventually established headquarters at Hunter Army Airfield, Georgia and Joint Base Lewis-McChord, Washington, respectively.
3rd Battalion, 75th Infantry (Ranger), and Headquarters and Headquarters Company, 75th Infantry (Ranger) received their colors on October 3, 1984 at Fort Benning, Georgia.
On February 3, 1986, World War II Battalions and the Korean War lineage and honors were consolidated and assigned by tradition to the 75th Infantry Regiment. This marked the first time that an organization of this size had been officially recognized as the parent headquarters of the Ranger Battalions.
After our nation was viciously attacked on September 11, 2001, Rangers were called upon to lead the way in the Global War on Terror. Due to the changing nature of warfare and the need for an agile and sustainable Ranger force, the Regimental Special Troops Battalion (Provisional) was activated July 2006 and made a permanent part of the 75th Ranger Regiment October 16, 2007
The 75th Ranger Regiment continues to take the fight to the enemy, in denied areas, every day, living the Ranger Creed.
Rangers Lead the Way!