One of the important chapters of post-Independence Indian Railways was the somewhat complicated task of building a new rail connection with Assam (and the rest of North-Eastern India) which had been broken when East Pakistan was formed. Here is the story pieced together and originally created as a ppt presentation in early 2011 at a convention of the IRFCA (Indian Railways Fan Club Association).
See what suits you best:
Or you may prefer to see the presentation as a series of images: (Read left to right, row by row)
The stress is on what happened in 1947-50. Some mention has been made of subsequent developments but this is not to be regarded as a full account of railway construction in the Northeast after independence.