The first railway in the East Indies was a line from Semarang to Tanggung on the island of Java, opened in 1867. It was built to standard (1435mm) gauge, but this proved uneconomical for further extension on account of the terrain and expected traffic, and all further development was constructed to narrow gauge, predominantly 3ft 6in (1067mm).
At their greatest extent, there were railways on the islands of Java, Sumatra, Madura and Celebes (Sulawesi). By the early 21st century there remained a network of lines serving most parts of the densely populated island of Java, together with three unconnected groups of lines on Sumatra.
For details of railways on each of the islands, click on the map links.