Before the British, Punjab was mapped only in route itineraries and rough sketches. The Sikh state kept revenue records but not maps in the modern sense.
After 1849 the Survey of India extended the Great Trigonometrical Survey across the province and the Revenue Survey mapped every village. The village map, the shajra, showing every field with its khasra number, is the base document of Punjab's land administration and still is.
That means Punjab has field-level cadastral mapping going back to the 1850s and 1860s, revised at each settlement, for its entire area. Very few places in the world have that.
The pre-1947 map sheets covering both Punjabs are held in India, in Britain and in Pakistan, and the sets are incomplete in each.
The historical map of Punjab, showing what territory belonged to whom at what date, has to be assembled from these and from treaty texts, and no authoritative version exists.
That is the problem this project's own map is an attempt at, and it is stated here so that anyone using it knows what it is built on.
The Survey of India mapped the province in the nineteenth century and the one inch sheets from that survey are the best topographic record of pre-partition Punjab that exists.
The revenue survey worked at a different scale entirely, mapping every field in every village, and that record is the one people actually use.
The old survey sheets are held in India, Pakistan and in libraries abroad, and a great many are digitised. Setting them against current satellite imagery would show a century of change and nobody has done it systematically.