Somerset is considered a suburb if we're talking Twin Cities. So is Hudson, River Falls, and New Richmond, WI. It's only about 12 miles from Hudson, on the border, to the east city limits of St. Paul. Another 10 to Somerset. I lived in Hudson and worked in Somerset.
There isn't a Twin Cities or St. Paul Craigslist, only Minneapolis, which you can filter by county. Which is why it is posted like that.