The "High Lakes" in the Eagle Cap Wilderness are full of small Brook trout. Plan on eating them - nothing better. Take a selection of flies, including some small sz 16/18 dries and nymphs. Some lakes have so many fish that a wide variety of larger flies will also work.
7/13/17: Many lakes are now ice free, but check with USFS for latest reports. Aneroid Lake produced 54 trout (but, hey, who's counting) on flies for one young man - one day last week.