Hey Tony, Welcome to the hobby!
Rocks are where you find them, but it helps to read up and do as much research as you can about the area you are looking at. There's a whole lot of research to do but atleast now most of it is recorded in a video on YouTube so you don't have to read as much.
You've got some of the best geode collecting in the world right next to you up and down the Mississippi.
And look at the post about the "Ben Clement Museum" in the post below yours here. It should be at the top of your list!
And the lakes are great opportunities! I've seen lots of videos about collecting the shorelines and what to look for.
As a tumbler you should know all about Lake Superior agates.
And luck helps so Good Luck!
Joe