Where should I go fishing for Catfish in the cities?

If you're not trying to eat them, I recommend the Mississippi.

Ditto on the Mississippi. Below the Coon Rapids dam is usually a good spot.

From shore, just about anyplace you can cast into the Mississippi or the Minnesota.

Fort Snelling has good access to both rivers, if you're willing to walk a ways.

Hidden Falls is good, the confluence of Minnehaha Creek and the Mississippi can be okay (but way crowded at times).

Mill Ruins park (by the Stone Arch bridge in downtown Minneapolis) can be awesome for numbers of fish at the right time of year (usually early spring and fall).

There are a lot of other spots that I just haven't fished, but I would imagine that just about any city / county / state park along either river is going to be a good place to start.

Thanks for the info. I'll be sure to check the areas out.