The 506th Port Battalion, Transportation Corps was constituted in the Army on 23 February 1943 and activated at New Orleans Port of Embarkation on 25 May 1943. On 30 June 1943, it was reorganized into a Headquarters and Headquarters Detachment and the four lettered companies, A through D, were redesignated as the 282nd through the 285th Port Companies. The battalion served in the New Guinea Campaign, Leyte and Luzon. It was inactivated in the Philippine Islands on 25 January 1946.
The United States assumed a greater role in the ground war in South Vietnam during the summer of 1965. The first phase of the war was to build combat power around four major ports: Saigon, Cam Ranh Bay, Qui Nhon and Da Nang. This buildup deployed transportation battalions from across the active-duty posts in the United States. The second buildup would increase American troop strength in South Vietnam to 385,000 men and women and push combat units further inland to take the offensive against the enemy. This would require a significant increase in truck companies, battalions and group headquarters in order to sustain them. Since President Johnson was not going to activate the National Guard or Army Reserve, the nation instead had to increase the draft so the Army could activate more transportation units to meet the increasing requirements in Vietnam. On 1 June 1966, the Army activated the Headquarters and Headquarters Detachment, 506th Transportation Battalion along with the 54th Transportation Battalion (Motor), and 8th Transportation Group, commanded by Colonel J. P. O’Connor at Fort Lewis, Washington conveniently located near McChord Air Force Base.
The 506th Transportation Battalion, commanded by Lieutenant Colonel Porter, deployed to Okinawa where it fell under the command of the 2nd Logistics Command.
The 531st Transportation Company (Medium Truck) had left Fort Riley, Kansas on 28 November 1965 and arrived on Okinawa on 14 December where it was assigned to Headquarters, Fort Buckner. It was then attached to the 506th Transportation Battalion on 17 October 1966.
During 1966, the 531st Transportation Company participated in Naha Port Clearance on an around the clock basis, seven days a week. This unit provided direct support for Roll On/Roll Off ships, SS Transglobe, USNS Taurus and Comet, operating between Okinawa and Vietnam beginning in March 1966. This operation required approximately 30 special equipment operators be trained for loading and unloading. During the period of 1966 they logged in 474,857 miles and moved 302,224 tons of cargo.
During the first quarter of 1967, the company traded in its tactical M52A2 tractors for commercial International Harvester, Model 1890 Loadster, tractors. During 1967, the company logged 660,518 miles and moved 572,425 tons of cargo to Vietnam and back. During 1968, it logged in 718,830 miles and moved 669,883 tons of cargo.
The 506th Transportation Battalion was inactivated on 25 June 1968 and the 531st Transportation Company was placed under the Special Troops Fort Buckner for administrative purposes and under the Port Transportation Fort Buckner for operational commitments. On 15 January 1970, the company was attached to the Transportation Battalion (Provisional) of the 2nd Logistical Command. During the first quarter that year, the company traded in its International Harvesters for M52A2 tractors and initiated a rebuild program for the 12-ton M127 trailers. The programs were completed by the second quarter. During 1970 the company logged in 447,019 miles and moved 1,184,240 tons of cargo.