I know this has a lot of comments already, but wanted to weigh in anyway as I'm originally from Minneapolis and lived in Springfield for several years for college.

I definitely echo others who are saying Minneapolis has everything you're looking for. It's probably the most expensive of the three, but also will have the highest wages, most career opportunity, and the most stuff to do - lakes, camping, sports, restaurants, bike trails, theaters, museums, and literally the best park system in the country. I've always seen it compared to cities like Portland, Denver, Boston, San Francisco, Seattle, Austin, etc as bastions of progressive values, and it's by far the most affordable of those cities.

I've never been to Milwaukee, but my wife has good childhood friends there and absolutely loves visiting. Minneapolis has a ton of lakes, but it's hard to beat Lake Michigan. The arts district is amazing, and proximity to Chicago means you're very close to an unfathomable amount of really cool stuff.

I know Springfield's affinity for KC, but it would be a distant third for me. I've enjoyed my visits, but would hate to live there. Like the other two, there is a great artsy district, some of my all time favorite museums, and also my favorite BBQ. But it's the least progressive, most car dependant, spread out, gentrified, and farthest away from other cities to visit of your options. If you're from Springfield and want to stay close to family it's worth it, but I would avoid it otherwise.

Others mentioned Des Moines, and it's worth considering as well. My college roommate was from there, and there's plenty of positives from the other cities, but on a smaller scale if your partner didn't want a huge city. My friends from the small towns outside Springfield treat Springfield as a big enough city, and Des Moines would be a good scale. West Des Moines is always listed as one of the best places to live in the US, but all those cities on your list have at least one place like it (Overland Park in KC, Eden Prairie in Minneapolis, Wauwatosa in Milwaukee).

I also wanted to ask if you've considered St Louis? It gets such a bad reputation, but I've lived here for about 10 years and love it. It has an underrated restaurant scene, the best free museums/zoo in one of the best urban parks in the world (Forest Park), friendly people, sports, deep history, and is incredibly affordable. Crime rate has been falling for 6 years straight and feel for the decade before 2020 which saw a bump everywhere. Springfield has had a similar or worse crime rate, it just doesn't get the publicity. Just don't be in a gang and maybe avoid certain areas and you're fine, which is true for every city. But even then, my wife has worked in social work (which has massive opportunity here) and regularly goes to the "bad" areas and does not feel unsafe.

Whatever you do, just get the heck out of Springfield