Hollandsche IJzeren Spoorweg-Maatschappij

The first line constructed was a line following the straight route of the Haarlemmertrekvaart canal, connecting Amsterdam with Haarlem, which opened on 20 September 1839. The line was quickly expanded to follow the Leidsevaart canal and reached Leiden in 1842, The Hague in 1843, and Rotterdam in 1847. Because this line is the oldest line in the Netherlands, it is now known as the Old Line. This line was originally built to Dutch broad gauge 1,945 mm (6 ft 4+9⁄16 in), but was converted to 1,435 mm (4 ft 8+1⁄2 in) standard gauge in 1866.

The line started at the Amsterdam d'Eenhonderd Roe station on the west side of Amsterdam, across the street from the company's headquarters, and ran to the Delftse Poort station in Rotterdam. Aside from this line, the HSM constructed a number of other rail- and tramways in the Netherlands, mainly in the relatively densely populated Holland, such as the Staatslijn K (1860–1865), a line northwards from Haarlem to Uitgeest in 1867, and the line to Zandvoort (1881). But the HSM also exploited lines to other regions, such as Utrecht (where it connected to lines of the SS), Zutphen (past cities as Amersfoort and Apeldoorn) and Nijmegen. The HSM even exploited a line to Leeuwarden, which took passengers by boat over the Zuiderzee.

Economic woes caused by the First World War forced the HSM to start cooperation with the other Dutch railway company Maatschappij tot Exploitatie van Staatsspoorwegen (SS) to strengthen their economic position. In 1938, this led to the formation of the Nederlandse Spoorwegen.