Light House Island secrets

I may now also be on a mission to find the other light house Island tradegies that are usually fairly held secrets.  Why did they suddenly no longer need a light keeper of a pivotal island?

The two I currently know by heart pretty well

Green Island 1864.  I believe I have that year correct.

Snake island somewhere very remote in the ocean… ?  whatching a show and heard the story, now I am obsessed..