I don't have an exact date, but in talking with people who have been there a long time, I believe power was brought over to Rattlesnake (and also Sleepers) sometime in the late 60s. That's a long time.
Diamond Island still doesn't have power, but when we looked at property there a few years ago, we were told that the power company would have run a cable over to the island (at that time, a few years ago) for something like $100,000 or a figure like that. I think it worked out to be around $5000/lot. Apparently, the majority (or super-majority - I don't know how their association or whatever works) don't want power over there, and so the island has remained "dark". I thought it would have been kind of fun to set up a solar array and constructing various other methods of providing power
