Rail transport was first introduced in Myanmar in May 1877 with the opening of the Yangon to Prome line by "The Irrawaddy Valley State Railway" when Lower Burma was a British colony. Unusually for a British colonial railway, it was built to . Subsequent development was to the same gauge, though the Burma Mines Railway opened in 1906 operated on a separate gauge. In 1884, a new company, "The Sittang Valley State Railway", opened a line along the Sittaung River from Yangon to the town of Taungoo via Bago. After the annexation of Upper Burma following the Third Anglo-Burmese War of 1885, the Taungoo line was extended to Mandalay in 1889. Following the opening of this section, the Mu Valley State Railway was formed and construction began on a railway line from Sagaing to Myitkyina which connected Mandalay to Shwebo in 1891, to Wuntho in 1893, to Katha in 1895, and to Myitkyina in 1898. Extensions into southern Myanmar began in 1907 with the construction of the Bago-Mottama line. Passengers had to take a ferry over the Thanlwin River (Salween River) to Mawlamyaing.