The clue's in the name! In the early days of stamps, the railway system was easily the fastest mode of transport and was key to postal communication. Some countries allowed railway companies to charge for private carriage of mail and issue stamps for the purpose. Indeed, in Britain, the Post Office didn't provide a parcel service for many years and the railway companies filled that gap with a multitude of issues of labels. Related topics such as Travelling Post Office postmarks and railway poster stamps are also popular.