Free-living gorillas live only in Africa. There are two main kinds of gorillas: Western gorillas (Gorilla gorilla) and Eastern gorillas (Gorilla beringei).
Eastern gorillas live in Rwanda, Uganda, and Democratic Republic of Congo. There are two subspecies, Mountain gorillas and Grauer’s (or Eastern lowland) gorillas. There are approximately 700 Mountain gorillas, and several thousand Eastern lowland gorillas — down from about 17,000 in the 1990’s according to the World Wildlife Fund.
Western gorillas live in Cameroon, Gabon, Congo, Central African Republic, Angola, and Nigeria. There are two subspecies, Western lowland gorillas and Cross River gorillas. There are only several hundred Cross River gorillas left in the world, and as many as 100,000 Western lowland gorillas, but the latter population has decreased by approximately 60% in the past 20-25 years, due to poaching, habitat loss, and disease, according to the WWF.
Most captive gorillas live in zoos in the USA and Europe; all are Western lowland gorillas. Koko and Ndume, who live at the Gorilla Foundation in Northern California, are also Western lowland gorillas. There are roughly 600 gorillas in captivity throughout the world, as of 2013, with 300 of them living in zoos in North America.