This is a male specimen of the eastern Hercules beetle (Dynastes tityus), a species of rhinoceros beetle native to the eastern US.
I saw one of these only a handful of times growing up, and I was amazed each time.
I associate them with years when June is rainy, and the plants are fat and green. I think every one of these I have seen turned up the day after a night rain.
If I had any doubts about turning my lawn into an ecological oasis, this guy showing up would have convinced me.