Across MISSOURI ? route ?

When you do get up to Cedar Rapids, try to make a visit to the close by Amana Colonies. Very German. Great restaurants, shops and especially a terrific furniture and clock shop where you can watch the craftsmen make grandfather clocks. I used to drive up to the meat shop every December to get our Christmas ham. Of course, I also loaded up on brats, sausage, cheese, etc.

I believe they've now added a campground since I've been there last.

I take 71 out of Joplin to Kansas City I 35 to Des Moines and I 80 east. 71 up through MO and into KC is easy going and you can make good time if you want to.

Joplin to CR is one of those routes you don't have interstate all the way so you could go a bunch of different was.

As one who crosses Missouri several times a year from the Oklahoma-Kansas-Missouri corner to various points north and east, I would choose Bumpy's route to get to Cedar Rapids. I've found some good east-west alternatives to the Interstates, but not much in the way of north-south routes, particularly in NE Missouri and SE Iowa that move really well.

US-71 to I-35 takes you into the east side of Kansas City (you would use the east side of the loop to connect) where there will be some suburban traffic, but for Iowa destinations I see it as a necessary evil, to get to I-35.

I had been thinking of US-71 to US-54/US-24 which go diagonally towards the Mississippi at Hannibal. This goes through Lake of the Ozarks, and Hannibal is also an interesting visit, but that leaves no route north that I really like. Great River Road routing is interesting but takes you well east of Cedar Rapids. US-61 has been rough the past few times I've been on the section south of Hannibal, and carries quite a bit of truck traffic. I don't know it at all north of Hannibal.

If, you were in hurry I'd say your first option. But since you're not I'd go the 2nd option, but change one thing. 65 out of Springfield to 73 to 54. Either way you'll encounter a lot of small towns from I-44 to I-80 which IMP isn't bad.
I personally won't take the I-44 to 61 route to get to Cedar Rapids.

If you got the time Joplin to St Louis then 79 and follow the river up. If you want to explore St Louis then I would recommend Casino Queen RV Park just across the river from the arch and they have a shuttle that will take you to the metro link station beats driving.

I'd go up 71 to 35 to 80 to 380.
bumpy