Home » Travel » Wisconsin » The Great Divide Highway

The Great Divide Highway

© Peggy Hoehne

A very, very long time ago, when the earth was still being formed, a microcontinent rammed into the North American plate*. At that time the North American plate ended in what is now northern Wisconsin, because everything south of there had broken off millions of years earlier and drifted away somewhere.

When this new plate rammed into the North American plate it caused the tall Penokee Mountains to be raised up. About 1.2 billion years ago during the Keweenawan Rifting (rift- to split open; break) the Penokee and the parallel Gabbro Ranges were stood on end.

One of the layers of these ranges is a Quartzite/ Ironwood formation, which is much harder and more resistant to erosion than the layers to either side. This is what forms the summit line of the Penokee range. The Gabbro range is a slightly lower line of hills about three miles to the north of the other. Its summit is a granite type rock. The Penokee-Gogebic Range runs about 80 miles from Wisconsin into Michigan. It is only about a half mile to a mile wide. The Penokee Range is broken by numerous water gaps. The streams in these gaps, with the exception of three, run north toward Lake Superior.

In just the thirty miles between Montreal Creek and the Bad River there are nine water gaps. Because of the short distance these streams have to drop down from over 900 foot to Lake Superior, this is an area of deep, narrow gorges, rapids, and waterfalls. The Penokee-Gogebic Ranges form a Great Divide. We think of the Rocky Mountains or the Appalachians when we think of Continental Divides, but they do occur in other less publicized places. Northern Wisconsin is one of those places.

There is a Roadside Marker in the Chequamegon (SHO-WAH-MA-GON) National Forest south of Grandview on County D in Bayfield County and another on highway 13, 2 ½ miles north of the junction with Highway 77 in Ashland County. These markers explain to those passing by that this is a Great Divide and why.
• When a raindrop falls on the north side of the Divide it flows into Lake Superior, then east thru the Great Lakes into the St. Lawrence and finally into the Atlantic Ocean.

• When a raindrop falls on the south side of the Divide it flows into the Chippewa and Namekagon Rivers, then westerly into the Mississippi River and south to the Gulf of Mexico.

The copyright of the article The Great Divide Highway in Wisconsin is owned by . Permission to republish The Great Divide Highway in print or online must be granted by the author in writing.