All white tigers found in captivity come from one found in India!
The white tiger is a rare pigmentation variant of the Bengal tiger, which was reported in the wild from time to time in Assam, Bengal.
White tigers are distinct from the normal colouration in that they lack the phaeomelanin pigment that in the normal tigers produce the orange color. They still produce the other color pigment, eumelanin, and hence are not considered albino.
Compared to normal colored tigers without the white gene, white tigers tend to be somewhat bigger, both at birth and as fully grown adults.
All white tigers found in captivity come from one tiger named Mohan, found in India in the 1950s. Mohan was the founding father of the white tigers. This breed has been protected for several decades now by the Indian government, and it is expected to be kept safe as long as the government has the power to do so.