Do You Know Why Do Montana’s Rivers Flow North?

BUTTE, MT - What once started as a fun riff your dad used to make in the car on a long road trip across the Treasure state has turned into a question we've always wanted to know the answer to: 

Why do rivers in Montana flow north?

Get our free mobile app

If you've ever found yourself staring at a map of Montana, you may have noticed something unexpected: several of Montana’s rivers, like the Missouri and Milk, seem to defy the laws of physics and flow to the north.

But why do rivers in Montana flow north, when most people assume rivers should flow south, following gravity’s pull towards lower latitudes? Or, you know, something like that. As it turns out, nature doesn't adhere to our simple expectations.

Check out the obvious answer below, along with the Continental Divide's unexpected influence and the ancient glaciers that shaped our world today.

Blame It on the Rockies

Montana’s landscape is heavily influenced by the big and beautiful Rocky Mountains, one of the biggest factors shaping the direction of river flow. Rivers don’t flow south simply because of direction: they flow downhill, towards lower elevations.

In Montana, the highest peaks of the Rockies are in the west, so rivers like the Missouri and Yellowstone start in these elevated areas and flow towards lower ground, which in this case happens to be to the north and east.

The Continental Divide

Another key player is the Continental Divide, a fan favorite for us here in Butte. It’s like the ultimate watershed, as on one side, rivers flow west towards the Pacific, while on the other, they flow towards the Atlantic. Since parts of Montana lie east of the Divide, rivers like the Missouri flow north, then east, and eventually south, reaching the Gulf of Mexico.

Ancient Glaciers Shaped the Land

A little over 10,000 years ago, glaciers covered much of North America, including Montana. As they advanced and receded, they carved out river valleys and altered the landscape. In some cases, these glaciers redirected rivers to flow northward, forming new courses as they melted.

Following the Path of Least Resistance

In the end, Montana’s rivers are simply doing what rivers (and humans) do best: taking the easiest path downhill. With the Rockies towering to the south and west, northward is just the path of least resistance. So, the next time you see a river flowing north in Montana, you’ll know it’s all thanks to geography, glacial history, and a little help from our unsung hero, the Continental Divide.