North western part. It can be found as has been said before from other sources "north of the Missouri river" just look up some geologic maps on glaciation in Missouri and you can see where the basic boundary is. The bigger gold seems to come where 1. Current streams cross enriched glaciated streams or 2. Current streams cross moraine. Seems to work good here. In your area if you cross into Missouri and hit the far NE corner I have read that there is a state park/conservation area that was built around an old gravel plant that processed nothing but glacial gravels and they even used it for the county roads, metal detector anyone?? Really what I do is check streams for glacial rocks...anything but limestone and pan it to check. Bedrock/crevices best but a good sticky clay has actually been the best for me, gold sticks to it like glue and easy to find streaks. Also, where larger rocks tend to catch in a stream try digging at the head of the rocks where they start. I've found good sized gold in these areas.
