Why is North Sioux City in South Dakota and Not Iowa?

Most people in our area know that the Big Sioux River is the boundary between the states of Iowa and South Dakota. But, if you look at a map of the entire "Siouxland" area, there is a small triangle of land that looks like it should belong to Iowa, but it is actually firmly in the Mount Rushmore State.

This is the curious case of how North Sioux City ended up in South Dakota.

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Long before it was North Sioux City, the area was founded in the 1860s as McCook. It's widely believed to be one of the very first European settlements in the region. It even served as the original county seat for Union County until 1865. The town got its name from the nearby McCook Lake, an oxbow lake which was formed by the Missouri River.

In 1922, the town was renamed Stevens after WW Stevens, and was home to the legendary Sioux City Speedway, where iconic race car driver, Eddie Rickenbacker, wowed enormous crowds in the days leading up to WWI.

As the area grew and became more integrated with its larger neighbor to the south (Sioux City, Iowa), the community decided to officially become "North Sioux City" in 1951 to better reflect its role as the northern gateway to the Siouxland region.

Okay, now that we know how it got its name, why isn't it in Iowa in the first place?

The mystery of North Sioux City comes down to the Big Sioux River. When South Dakota and Iowa defined their borders in the mid-to-late 1800s, they used the center of the river channel as the official dividing line. But, here's the thing about rivers: over time, they change course.

Over the decades, the Big Sioux and the Missouri have shifted their banks a few times. North Sioux City sits in a unique "pocket" of land that stays west of the Big Sioux.

When South Dakota gained statehood in 1889, the border was locked in based on where the river ran at that time. So, even though North Sioux City is physically "tucked" into the corner of Iowa and Nebraska, it remains on the South Dakota side of that original water line.

While some may think it "belongs" in Iowa, being in South Dakota does give it one big advantage: Taxes... North Sioux City (and nearby Dakota Dunes) became a big-time draw for people working down south, in Sioux City, Iowa, who wanted to avoid Iowa's state income tax while living just a few blocks away from their jobs.

These days, North Sioux City has grown considerably, and while the name might still confuse your typical "passerby", the locals wouldn't have it any other way.