60 Years and 2 Sightings
The state of Alabama, USA just got a little treat.

In the 1950's, the state of Alabama, USA lost a precious resource to habitat loss. That resource, the snake Drymarchon couperi - or eastern indigo snake - was an apex predator in the longleaf pine forests of the region. Because of its loss, the forest became sick; the ecosystem suffered, and species populations were negatively affected.
But in 2006, that began to change. A local conservation group decided to reintroduce the snake into its native range with the hope of eventually establishing a population of 300. They launched the program in the Conecuh National Forest where, in 2020, the species was spotted by accident for the first time in over six decades.
And now it looks like their efforts are succeeding. Just several days ago a second individual was sighted in the region. Its small size and lack of a tracking tag indicated that it was a wild-born snake and not one of the original generation first released into the wild.
“The snake ... indicates that the project is resulting in some thriving and reproducing indigos — just what we wanted!" said the Alabama Department of Conservation and Natural Resources in a statement. The new discovery indicates the the species is beginning to do well, and hopefully it won't be long before they're thriving. Not only is this good for the species, but it also means salvation for the forest. Once the population reaches a few hundred, the forest will begin to heal.
Are there more? Possibly. Despite its great length of well over 2.3 meters (7.5 feet), D. couperi has a talent for stealth and hides very well in the forest underbrush, and thus is not easily seen. That's why it's rather impractical to go out looking for these black and iridescent-blue snakes; sightings are typically accidental.
Oh, and don't worry. This one's not venomous.

Look at that pretty little face!
Credit: Ben Gartolotti, Wikimedia Commons, CC-BY-SA.

Slitherin' through the grass