For anyone researching a Punjab place, the material that exists and is reachable, mostly free.
District gazetteers, one per district, revised several times between the 1880s and the 1930s, covering history, castes, crops, trade, fairs and notable places. Most are digitised.
Settlement reports, made at each revision of the land revenue, recording village-level landholding, tenure, custom and cultivation in extraordinary detail. Less digitised and worth the trouble.
The census reports from 1881 onward, with village directories listing every settlement and its population.
The Imperial Gazetteer of India, the Punjab volumes, for a summary view.
For Sikh history: Bhai Kahn Singh Nabha's Mahan Kosh, Ganda Singh's published document collections, Rattan Singh Bhangu's Prachin Panth Prakash, and the Panjab Digital Library's scans.
For the twentieth century: the Punjabi and English press files, the Desh Bhagat Yaadgar Hall collections at Jalandhar, and court and commission records.
None of this is secret. Most of it is a search away. Almost nobody uses it, which is why so much of what is repeated about Punjab is repetition rather than research.
The gazetteers, the settlement reports, the census volumes and the district histories from the colonial period are almost all digitised and free, and they are the backbone of this site.
The Sikh sources, the janamsakhis, the gurbilas literature, the rehatnamas and the vaars, are published in Punjabi and mostly untranslated.
What is missing is anything written by ordinary Punjabis before the twentieth century. The record is administrative or devotional and there is very little between.