Marine Two

Marine One is the call sign of any United States Marine Corps aircraft carrying the President of the United States. It usually denotes a helicopter operated by Marine Helicopter Squadron One (HMX-1 "Nighthawks"), either the large Sikorsky SH-3 Sea King or the newer, smaller VH-60N "White Hawk". A Marine Corps aircraft carrying the Vice President has the call sign Marine Two.

The first use of helicopters for transporting the President was in 1957, when President Dwight D. Eisenhower traveled on a Bell UH-13J Sioux. The President needed a quick way to reach his summer home in Pennsylvania, as Air Force One could not land at the White House or the summer home. Eisenhower instructed his staff to look into alternative modes of transportation and a Sikorsky UH-34 Seahorse helicopter was commissioned. The early aircraft lacked the "creature comforts" found on its modern successors, such as air conditioning and toilets for in-flight use.

In 1958, the H-13 was replaced by the Sikorsky H-34, and in 1961 by the VH-3A. Not long after the mode of presidential transport was introduced, presidential aides asked the Marine Corps to look into the White House South Lawn as a helicopter landing zone. Ample room was present, and the protocol was established.

Until 1976, the Marine Corps shared the responsibility of helicopter transportation for the President with the United States Army. Army helicopters used the call sign Army One while the president was on board. The VH-3D entered service in 1978. The VH-60N entered service in 1987 and has served alongside the VH-3D. Improvements were made to both types of helicopters since their introduction to both take advantage of technological developments as well as to meet new mission requirements. However, by about 2001, it was clear that so much extra weight had been added to the helicopters that mission capability was being reduced and few new improvements could be made.

...
Wikipedia