The First Opium War (Anglo-Sino War) ends: Chinese and British emissaries sign the Treaty of Nanking, ceding the island of Hong Kong to the United Kingdom forever, and granting special trade concessions to the British, by opening six ports to British trade.
[added 1/15/2022] Thanks to Jim Lorenz for this entry.
Great Britain gave it back in 1997, so even “forever” has limits in human diplomacy. –– JL
Subsequent Events:
References:
A Short History of the Opium Wars
www.calyx.net/~schaffer/heroin/opiwar1.html
The Anglo-Chinese Treaty of Nanking (1842)
web.jjay.cuny.edu/~jobrien/reference/ob24.html