Suggestions -- National Parks along the way to South Dakota

My friends and I will meet in Sturgis. I am leaving a couple of days earlier and would like to take a leisurely drive and stop at a couple of sites before meeting with them. We are going to take in the parks around Sturgis, Crazy Horse, etc. so I don't need suggestions in the area of Sturgis.

Ideas?

Unsure what direction you are coming from and not a National Park, but one of the best parks in the Black Hills region is a state one:  Custer State Park.  There are buffalo herds and many other wild animals that are usually visible as you take the internal Wildlife loop road.  IRC, the loop road takes about 1-1/2 hour or so.  

Nearby is Wind Cave National Park, one of the oldest national parks--we have managed to miss the guided tours through the caves every time we have been in the area.  

We will be seeing Custer and Wind Cave during the week. I am leaving from Maplewood, going west. Looking for sites along the way.

If you are driving west through Pennsylvania, you might want to make a slight detour to the northern panhandle of West Virginia. We visited the state once on vacation, but didn't make it into this area, although I had really wanted to (we stayed around Seneca Rocks and  Blackwater Canyon, which are cool, but closer to Maryland, and not really on your way). 

The northern panhandle is the 4 counties that border western PA - it has the Grave Creek Mounds (Moundsville), which is a site dating back to the Adena peoples of the area, 3rd century BC (or BCE, if you prefer). There are also a number of islands in the Ohio River, called the Ohio River Islands National Wildlife Refuge, which are supposed to have lots of different kinds of animal life - birds, otters, different fish. I also remember reading something about a small area there with a unique microclimate, but I wasn't able to find anything on it quickly. If it interests you, you  might be able to find the info.

Ive done the western SD trip a couple of times from different directions. Depending on whether you are looking to camp or do motels, here are some ideas. This time of year, the northern routes are probably a nicer more temperate trip. Laid these out along a westerly direction below.

Cheat River is a bit south of a direct route but stunning.

Athens OH is a nice stop about 8 hours from here, river town near the WV border. College town.

Dunes in northern Indiana has some beautiful scenery and wildlife- camping is fun here. 

Madison WI and Rochester MN both have some excellent restaurants to try and some wonderful lakes nearby. Walleye or wild fowl make awesome dinner choices in the area.

John Deere world headquarters is in Moline IL and has a museum/display of their equipment, kind of an oddly interesting visit. 

Quad Cities area has a whole riverfront thing going on along the Mississippi/Rock confluence. I found the Iowa drive to be a bit long. We camped at several state parks, and found them to be quite open- not forested like here.

The Corn Palace in Mitchell SD can be a fun kitch diversion. I pretty sure they renew the design at the end of August each year. Wall Drug Store in Wall SD is another one of those kind of tourist stops.

Yeah, the guys want to go to Wall Drug. Seems they give out free ice water.

There is a lot of Lewis & Clark stuff in that area/direction.  I can't give you many specifics but you should check it out.

Madison (Wisconsin) is a nice town if you are looking for a place to sleep along the way.

http://www.nature.org/ourinitiatives/regions/northamerica/unitedstates/ohio/placesweprotect/edge-of-appalachia-buzzardroost-rock-trail.xml

The microclimate that OP mentioned in a post above is located in the Edge of Apppalachia Preserve.  It's not far from the Islands in the River park.  If I only had time to do one hike in Ohio, it would be to Buzzard Roost Rock.  The view is breathtaking! 

I'm not looking at a map, so not sure how far out of your way...

Gettysburg (though I imagine you've already gone there).

Driving up the Mississippi "River Road" between Wisconsin and Minnesota is beautiful and (usually) quiet.  Some good birding spots, too, or so I'm told.