It branches from the Bloemfontein–Bethlehem line at Marseilles, Free State, and runs in a south-easterly direction for 24 kilometres (15 mi) to the Caledon River. After crossing the river, which serves as the border with Lesotho, the line runs for 1.6 kilometres (1.0 mi) through an industrial area of Maseru, serving the city's station and various factories and depots. The line is owned by Transnet Freight Rail of South Africa; it has freight service but no regular passenger trains.

Construction on the Bloemfontein–Bethlehem railway line, intended to link the Orange River Colony (as it was then known) with the port of Durban, began in 1902 under the direction of the Central South African Railways. By June 1904 it was open from Bloemfontein as far as Modderpoort. In order to make the line viable, it was desired that it should serve Maseru, but for the sake of economy it was decided to build the main line along a shorter route and connect Maseru by a branch line. The line from Marseilles to Maseru, including a new bridge over the Caledon River, was opened on 18 December 1905.

• History of rail transport in Lesotho
• Rail transport in Lesotho

• Boonzaaier, J.N.C (2008). Tracks Across the Veld. p. 245. ISBN 978-0-620-41711-2.