First Anglo-Sikh War ends — the hills pass to the British

The Treaty of Lahore (9 March 1846) transferred the Sikh hill possessions to the East India Company. Kangra, Kullu, Lahaul and Spiti were formed into the district of Kangra under Punjab, with headquarters first at Kangra and later at Dharamshala.

This is the administrative fact behind 1966: because Kangra was made part of Punjab in 1846, it had to be transferred to Himachal Pradesh by the Punjab Reorganisation Act a century and a quarter later.