Got this guy within the downtown St. Paul section of Sippi pool 2 - a baby 12lbs. We also got a 13lbs, 25lbs, and we snapped off a possible 40lbs+. You don't have to travel far. Flatheads don't succumb to fishing pressure like other fish and though there are barges and lots of people in metro St. Paul, flats don't give a shit and do not fear us.
Harriet Island. There are many booze cruiser boats and couples walking around. I highly doubt any cops kick people out of there until after 2am. I went there once early season in May and stayed until 12:30am - no cops. I reckon most of you would venture beyond 12am anyway.
494 bridge boat launch at Hardman Ave and Vonderosa. Technically, it's a boat launch and not a park and the regulars who go there at fishingminneso
ta.com forums have never been kicked out. Expect people there but the whole damn shore is fishable so you'll never run out of space.
Grey Cloud Island in Cottage Grove. So many people during the day but night falls and there's two cars and you'll have the place by yourself. Fish the west bridge because there's a deep pool that is over 15'. You probably have zero chance of flats here though as it's too backwater from the main river channel.
Lion's Park - you'll be fishing a bay area so it's hit or miss but it's right there by the river channel so you shouldn't do too bad.
These places have visitors daily. Arrive late like after 9pm so people and boats are gone. Besides, flats will almost never move around during the day. Keep in mind that where people were catching flats in May and June, those areas are dried up by now because water level has been low since late July.
I would say wait 2-3 more weeks until it really gets cooler - that's when I'm going. This will force flatheads to move around and you'll get them in shallow water like back in May and June. Good luck!