From Wikipedia:

Tea planting in the Indian district of Darjeeling began in 1841 by Archibald Campbell, a civil surgeon of the Indian Medical Service. Campbell was transferred as superintendent of Darjeeling in 1839 from Kathmandu, Nepal. In 1841, he brought seeds of the Chinese tea plant (Camellia sinensis) from Kumaun and began to experiment with tea planting in Darjeeling. The British government also established tea nurseries during that period (1847). Commercial development began during the 1850s. In 1856, the Alubari tea garden was opened by the Kurseong and Darjeeling Tea company, followed by others.

Adulteration and falsification are serious problems in the global tea trade; as of 2004, the amount of tea sold as Darjeeling worldwide every year exceeds 40,000 tonnes, while the annual tea production of Darjeeling itself is estimated at only 10,000 tonnes, including local consumption. To combat this situation, the Tea Board of India administers the Darjeeling certification mark and logo.