The Scottish Midland Junction Railway was authorised in 1845 to build a line from Perth to Forfar. Other companies obtained authorisation in the same year, and together they formed a route from central Scotland to Aberdeen. The SMJR opened its main line on 4 August 1848. Proposals to merge with other railways were rejected by Parliament at first, but in 1856 the SMJR merged with the Aberdeen Railway to form the Scottish North Eastern Railway. The SNER was itself absorbed into the larger Caledonian Railway in 1866. The original SMJR main line was now a small section of a main line from Carlisle and central Scotland to Aberdeen.

The Aberdeen Railway was a Scottish railway company which built a line from Aberdeen to Forfar and Arbroath, partly by leasing and upgrading an existing railway.