Modern opossums are not as old as people used to think. In fact, they only date to about 20 million years ago. That is much younger than the "living fossils" they are sometimes described as being.
Opossums evolved in South America. That is where most of the sixty-five species of this animal live. In North America, there is only one opossum species, the Virginia opossum. Its Latin name is Didelphis virginiana. It is native to North America.
Opossums are New World mammals. In the United States, they are often called possums. However, this is a misnomer. Possums are separate animals native to Australia and New Guinea. Both are marsupials, but they come from completely different families.