Iowa’s M and M Divide

Iowa might not have the Continental Divide, the mountainous line that determines whether the rivers of the nation run toward the Pacific or Atlantic Oceans.

But we have our own M and M Divide, marking the line for Iowa watersheds toward the Missouri River on the west or the Mississippi on the east.

That dotted line, from roughly the NW corner of the photo to the SE, marks the M and M Divide.  Knowing that there’s a sign marking it just west of Guthrie Center, I wanted to know where it runs through the rest of Iowa.

Highway 30: This sign and rock, just east of Arcadia, population 525, shows its location in Carroll County. It’s along the historic Lincoln Highway.

Highway 44: As you drive west of Guthrie Center, you will notice the road climbs steadily higher until you reach the point where a marker announces that this is the “Missouri-Mississippi Divide, Elevation 1440 feet.”

Aunt Darlene, Sis Gloria, Mom (Doris) at the M and M Divide, Highway 44 between Audubon and Guthrie Center. June 19, 1995. Gloria drove, I took photos.

Interstate 80: According to a local, the M and M divide runs through the middle of Adair. “If you take the highway north from Exit 76 on Interstate 80, you are literally driving on it. It’s very close to the water tower with the happy face.”

Southern Iowa: Lorimor, Union County, touts its lofty spot on the M & M Divide.

Even the water draining to the Missouri River eventually ends up in the Mississippi River.

World Atlas map

Here is a better version of the map of the Drainage Basins of Iowa, showing where the M and M Divide runs through the state.


  1. That’s a cool bit of info! I learned a lot about watersheds in my geographic information science courses, but didn’t really consider other major divides.

    • I knew that Minnesota has watersheds that go three directions, but guess I was surprised that Iowa has a definite line through places I’ve been.

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