In the south, in particular, it was very common to have the kitchen in an out-building. Many middle-class women had household help of some sort as well. Where I live the kitchens were in the house, but I've lived in many other places where the kitchen would be in an out-building. I've lived in many old houses, and most of them had kitchens outside of the house originally (this one had old coal/wood stoves and cooked in the house as far as I know).
It also was done because of fire hazards. In other words, if the kitchen catches fire, you won't burn the house down! You'll just burn the kitchen shack down.
I happen to have an un-air-conditioned kitchen. There are only 6 weeks or so a year when it is a problem, but we have learned summer food and winter food, something we really didn't think about when we lived in central air. Chili, stews, and long-cooking soups are NOT summer dishes. While a part of me would like to retrofit the place and have central air, another part of me likes the back-to-nature part of this. In the summer we cook out or do a lot of salads and quick foods (stir fries, etc). We do have window A/C units in the back parlor, our bedroom, and our guest room. BUt learning about seasonal cooking is really brought home.
You'll have to let us know if you do go to the Des Moins place. I might add that their market day and "Taste of ..." are great.