Because of its location and how it was formed from inland sea to a glaciated region to the place it is today, Minnesota is a unique place containing many lakes and is the meeting place of four biomes.
The starting point of my Sylvaeon campaign is partially based upon the land that I love :)
I have populated the initial hex crawl with many of the native flora and fauna of Minnesota. The weather patterns mimic those occurring seasonally.
The flow and joining of the Drake's Wash & the Broken Arrow rivers in this starting area are based upon the real world confluence of the Minnesota & Mississippi rivers. The PCs have encountered these large rivers already. I used a riverside cliff cave in the last session based on those that are on the banks of these rivers. One encounter took place in a sink hole, like the ones that are present in various parts of the state.
Hex crawls and world building do not always entail reinventing the wheel. Using what is in the real world can ease the process greatly.
Remember the Giant Beaver in the Monster Manual? We had those things here.In fact, the most complete skeleton of a giant beaver was unearthed right here in Minnesota. The PDF linked below talks about some of the giant mamals of the past that roamed the state. I am itching to toss some megafauna at my players ;)