This is the South Western edge of the "Lyme Dome," in Old Lyme, Connecticut. If you want to find the rest of this rock, you'll have to go to Africa.
It all started a few hundred million years ago when six continents crammed together to form Connecticut. With "Game Of Thrones" names like Avalonia, Gander and the enormous supercontinent, Pangea, these land masses eventually broke apart and moved away from each other. But, like that shirt you left in your ex's closet and the framed photo of the two of you in Fiji that's buried at the bottom of a box in your basement, each left something behind with the other.
The "Lyme Dome" was formed when Gander collided with Avalonia. Gander, through no fault of its own, was pushed beneath Avalonia. (I want to be clear on this. It had nothing to do with being weak. Maybe Gander was trying to allow Avalonia to discover itself and flourish.) This vertical piling of rock created the "Dome," whose core is now located in the village of Old Lyme.
When the continents began drifting apart (which can happen even after you spend two months of your salary in Fiji) Avalonia and Gander were both severed, with parts of each shifting east to form the European and African continents . . . while the rest of us got left behind (but not abandoned, according to my therapist) in North America.
After 400 million years, I guess I should let it go.