The Penokean orogeny was a mountain-building episode that occurred in the early Proterozoic about 1.86 to 1.83 billion years ago, in the area of Lake Superior, North America.
It extends east from Minnesota to the Grenville orogen near Lake Huron and south to the Central Plain in Wisconsin.
First an island arc called the Pembine-Wausau terrane collided with the ancient North American craton along with volcanoes formed in its back-arc basin.
Hundreds of millions of years later, the Keweenawan Rift occurred in the same area creating the basin that would eventually become Lake Superior.
The remains of this orogeny can be seen today as the Iron Ranges of Minnesota and Ontario, the Northern Highlands of Wisconsin and the Upper Peninsula of Michigan.