Hanko is the southernmost town in Finland. Hanko has a seaport which, thanks to its location, can be used for the longest possible time during the sometimes very severe, and frozen, Finnish winters.
Because all the other Finnish seaports might be frozen solid during the winter, there was an anticipation for a large amount freight transit traffic. As such, a decision was made to privately fund the 149 km (92.5 mile) railway from Hanko to the Finnish State Railways' Helsinki-Hämeenlinna line, with the connection at Hyvinkää.
Work on the new railway began in 1872 with the inaugural run being on October 8 1873. Unfortunately, owing to insufficient funds, the private company soon got into financial trouble. Facing almost certain liquidation, the railroad company was sold to the Finnish State Railways in 1875.