Not 6, but William Watson is responsible for Interlachen, Minikahda, and WBYC all in the Twin Cities. A pretty good trifecta for a smaller market.
Or, another way to look at it is that Ross is largely responsible for five terrific courses in Minnesota, having redesigned Minikahda and Interlachen to the point where there's not much Watson left, as well as redesigning most of Willie Park, Jr.'s Minneapolis GC, Bendelow's Northland CC and designing Woodhill CC, which is largely untouched. Those inclined to do so can also give him credit for some undetermined work at WBYC.
Minnesota is not the population center that you would expect to find a half-dozen courses by one prominent architect, but Ross worked there a lot, and we are also fortunate to have outstanding courses by Tillinghast, Raynor, Stanley Thompson and Robert Trent Jones.