Is North Dakota more similar to Saskatchewan or Manitoba?

[King of Kensington]

Which Canadian province (the southern half at least) is North Dakota more similar to?

More of ND's lies closer to Manitoba and they were settled around the same time.  But the majority o Manitoba's population is in Winnipeg, Canada's "gateway to the west" and Manitoba also some Canadian Shield territory bordering Ontario.

Saskatchewan is more rural and has a historic "prairie populist" tradition, both have also seen resource booms.  However Sask is unambiguously Western Canada (Manitoba basically is too, but is also a "gateway") while ND is only "western" in the less populated parts.

[TDAS04]

I'd say Saskatchewan, since it lacks a city as big as Winnipeg.

North Dakota is the US state most similar to Saskatchewan (lack of big cities, lack of mountains, so much wheat), while Alberta is similar to Montana (at least in topography), and Manitoba is a little more like Minnesota (more forest, Winnipeg being the equivalent of the Twin Cities).

[Hatman 🍁]

Saskatchewan, easily. I agree, Manitoba is like Minnesota.

[evergreenarbor]

Saskatchewan, easily. I agree, Manitoba is like Minnesota.

[King of Kensington]

How much of Minnesota can really be thought of as Great Plains?

[muon2]

How much of Minnesota can really be thought of as Great Plains?

All of the Red River valley and the western part of the Minnesota river valley would qualify as Great Plains. Those areas lack the lake and woods character that typifies MN from the Twin Cities north to Canada and west to the beginning of the Red River plain from glacial lake Agassiz. Southeast MN is part of the driftless zone along the Mississippi.