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From December 2011 it is used by all direct trains from Amsterdam to The Hague, and all direct supplement-free trains from Amsterdam to Rotterdam except those through Woerden.
It contains the oldest railway line in the Netherlands, and follows the old horse-drawn boat (Dutch: trekschuit) canal route from Leiden via Haarlem to Amsterdam-Sloterdijk. It was opened between 1839 and 1847 by the Hollandsche IJzeren Spoorweg-Maatschappij. The oldest section, opened in 1839, led from Amsterdam to Haarlem. Leiden and The Hague were reached in 1843, and the final section from The Hague to Rotterdam was opened in June 1847.
The opening of the Weesp–Leiden railway (1978) and the Amsterdam–Schiphol railway (1986) provided a shorter connection from Leiden through Schiphol Airport to Amsterdam. Nevertheless, the old line via Haarlem has remained an important railway line.
- De Bosch Kemper, M.J. (1865). Handleiding tot de kennis van de wetenschap der zamenleving en van het Nederlandsche staatsregt (in Dutch). Amsterdam: Johannes Müller. p. 883.
- "English summary". Spoorzone Delft.