This includes part of a book which was not published. It may be of interest to some who are interested in the NWR at the time of Partition and later.
It should be noted that (essentially) the present Delhi, Ambala and Firozpur divisions fell in India and the rest of the NWR fell in Pakistan.
This is the official map from the “History of Railways” in 1937.
I don’t think there was any significant change from this point to 1947, apart from realignment which shifted the junction point at Ruk to nearby Habib Kot.
Apart from this, part of the metre gauge Jodhpur Railway (one time Jodhpur State Railway) beyond Munabao to Hyderabad (Sind) fell in Pakistan.
A similar official map from 1937:
The line from Mirpur Khas to Nawabshah via Khadro was completed later (in 1939).
Note the “frontier” stations at Phulad, Chilo, Sujangarh and Kuchaman Road.
Initially the NWR name continued to be used in Pakistan until 1961 when it became PWR and later PR. The metre gauge lines of the ex JoR were included in the NWR.
In India, the ex-NWR portions initially were a separate system called the East Punjab Railway, which soon became part of the Northern Railway. The EPR had joined the old EIR at Saharanpur and Ghaziabad.
However, the Saharanpur-Shahdara NG line was part of neither but continued to be owned by Martin & Co (later Martin Burn) until it closed in 1970.
The remaining part of the Jodhpur State Railway in India soon became the Jodhpur division of NR, and still later in the new NWR (HQ Jaipur) which has no connection whatsoever with the old NWR.
(Partition in the East was also quite complicated, so we leave that for another day).
Here is the extract of the unpublished book by Ken Staynor who is no more:
Breakup of the North Western Railway and the Anglo-Indian community