This article describes the Caledonian Railway from its conception down to the year 1850. In the 1830s and 1840s much thought was given to building a railway from central Scotland to join the growing English railway network. The hilly terrain and sparse population of the Southern Uplands made the choice of route contentious. The original route is a principal main line today, subject to the modifications approaching Glasgow, and later improved terminals there and in Edinburgh. The route is electrified and forms the northern section of the West Coast Main Line railway.