Côn Sơn Island Côn Sơn Island ( Vietnamese " Côn Sơn " ) , also known as Côn Lôn ( Khmer : Koh Tralach ) , is the largest island of the Côn Đảo archipelago , off the coast of southern Vietnam . The island is also known after its Malay name as Pulo Condore ( " pulo " as a corruption of " pulau " , meaning " island " ) , while its French variant Poulo Condor was well known during the times of French Indochina . Marco Polo mentioned the island in the description of his 1292 voyage from China to India under the name " Sondur " and " Condur " . In Claudius Ptolemy ' s " Geography " they are referred to as the " Isles of the Satyrs " . Early modern era . In 1702 , the British East India Company founded a settlement on the island of Poulo Condor off the south coast of southern Vietnam , and in 1705 the garrison and settlement were destroyed . In 1787 , through the Treaty of Versailles , Nguyễn Ánh ( the future Emperor Gia Long ) promised to cede Poulo Condor to the French . In exchange Louis XVI promised to help Nguyễn Ánh to regain the throne , by supplying 1 , 650 troops ( 1 , 200 Kaffir troops , 200 artillery men and 250 black soldiers ) on four frigates . In 1861 , the French colonial government established Con Dao Prison on the island to house political prisoners . In 1954 , it was turned over to the South Vietnam ese government , who continued to use it for the same purpose . Notable prisoners held at Côn Sơn in the 1930s included Phạm Văn Đồng and Lê Ðức Thọ . Not far from the prison is Hang Duong Cemetery , where some of the prisoners were buried . “ Tiger cages ” . During the Vietnam War , prisoners who had been held at the prison in the 1960s said they were abused and tortured . In July 1970 , two U . S . Congressional representatives , Augustus Hawkins and William Anderson , visited the prison . They were accompanied by Tom Harkin ( then an aide ) , translator Don Luce , and USAID Office of Public Safety Director Frank Walton . When the delegation arrived at the prison , they departed from the planned tour , guided by a map drawn by a former detainee . The map led to the door of a building , which was opened from the inside by a guard when he heard the people outside the door talking . Inside they found prisoners were being shackled within cramped “ tiger cages ” . Prisoners began crying out for water when the delegation walked in . They had sores and bruises , and some were mutilated . Harkin took photos of the scene . The photos were published in " Life " magazine on July 17 , 1970 . The prison on Côn Sơn Island was closed in 1975 , when North Vietnam ( now unified as Vietnam ) toppled the South Vietnamese government , in the wake of the withdrawal by the United States and its allies ( South Korea , Australia ) from the Vietnam War . The facilities were reopened some years later however , to temporarily incarcerate boat people captured by local coast guards until the late 80s . Along with the earlier disclosure of the Mỹ Lai massacre , and the later disclosure of the Pentagon Papers , the revelation of the conditions and purpose of Côn Sơn Island prison led more Americans to believe that supporting the South Vietnamese government was improper , adding to the opposition to the Vietnam War . Recreations of tiger cages can be seen today at the War Remnants Museum in Ho Chi Minh City LORAN Station Con Son . At the request of Secretary of Defense Robert McNamara , the U . S . Coast Guard started pre - construction plans for a chain of Loran - C radio stations to serve southeast Asia 15 January 1966 in support of Operation Tight Reign during the Vietnam War . The actual construction of Station Con Son began during April with the delivery of construction materials by and award of construction contracts to Morrison - Knudsen Corp . and Brown and Root Company . Station Con Son was one of five stations in the southeast Asia chain and was designated SH - 3 Yankee . It consisted of a tower , transmitter equipment buildings , fuel tanks , generators and barracks for personnel located on the north end of Con Son Island . The personnel complement for the station was two officers and 23 enlisted men . After commissioning on 2 September 1966 the station began the testing phase of operations and the five station chain was fully operational by 0400 on 28 October , just nine months after the initial request from the Department of Defense . The station provided , along with its sister stations in the chain , signals that allowed aircraft and ships to receive accurate all - weather positioning data for navigation purposes . During January 1973 the operation of the station was turned over to civilian contractors who were responsible to the United States Coast Guard for all functions of the station . The coast guard continued to supply logistical and technical support on an as needed basis . When the fall of the South Vietnamese government was imminent , Station Con Son was directed to stay on the air until the last possible minute to provide navigation signals to aircraft and ships fleeing South Vietnam . Station Con Son stayed on the air until 1246 local time on 29 April 1975 after the crew oversped the generators and damaged critical pieces of electronic gear .