The Don Det–Don Khon railway (sometimes spelled "Don Deth–Don Khone") was a -long narrow-gauge portage railway on the islands of Don Det and Don Khon, part of the Si Phan Don (Four Thousand Islands) archipelago in Champasak Province of southern Laos. Built by the Mekong Exploration Commission, the railway was operated by the Lao State Railway. It opened in 1893, and closed in 1940 or 1949. The railway was initially laid to gauge, and may have been partially (or fully) converted to . It facilitated the transportation of vessels, freight and passengers along the Mekong River. The Don Det–Don Khon islands railway was the only railway built, opened and operated in Laos until 2009, when a line was opened between Nong Khai, Nong Khai Province in Thailand and the Thanaleng railway station in Dongphosy (near Vientiane). History Background The French colonial administration of Indochina was determined to use the Mekong River for a route into China, and to help counter British colonial expansion in Upper Burma. The governor of Indochina saw the Mekong as "the main point of connection between the different countries of French Indo-China (Cochin-China, Cambodia, Laos and Tonkin), which will be able to communicate with each other through it". The main obstacle was in southern Laos, where the river divides into several channels with rapids (known as the Khone Phapheng Falls) at the Siphandon Islands. Attempts in 1891, 1892 and 1893 to scale the falls failed; accounts exist of steamships with "engines roaring and boilers near bursting, with hundreds of men hauling from the rocks on ropes and others pushing from the decks with pikes", and one vessel "allegedly wriggled up a narrow water-slide to within fifty metres of the top before the attempt had to be abandoned". Alternative modes of transport were necessary. One idea came in the form of Herbert Warington Smyth, a British tidal expert living in Siam, suggested that a tramway or canal with a series of locks should be built around the falls; a canal "would satisfactorily cripple the French economy, costing about the same as the Manchester Ship Canal yet never carrying more than one ten-thousandth of its tonnage". The French settled on a small portage railway across the islands of Don Khon and (later) Don Det, which would allow specially-designed vessels to be dismantled, transported on the railway, reassembled and launched further upstream. Development The first railway was laid on