Driving from St. Charles, MO to Springfield, MO

I've charged at several RV parks in Minnesota. I just show up. I drive through the park to see if there are any open spots/NEMA 14-50 outlets; in the summertime, it's not uncommon for all spots to be full, and if that's the case, I just move on. But if there is a available one, verify that it's a NEMA 14-50: I've seen quite a few RV parks that only have 30 amp circuits (NEMA 10-30, I think). While there is an adapter from Tesla to go with your charger for this, at 30 amps it's so slow that I don't think it's worth the bother. Anyway, assuming the open spot has a 50 amp circuit, go to the host site or whoever manages the campground and tell them you have an electric car and would it be okay if you plugged in for an hour or so, and TELL THEM YOU WILL PAY FOR IT. I usually offer $2 -$5 per hour. You might have to explain it a couple of times because most people just don't know anything about EVs. Sometimes the person has initially declined saying the spots are reserved for RVs; I persisted, repeateding that I would pay for the electricity, pointing out that I'll only be there for an hour or so, and they've always relented after they think about it a bit. And that's if they resist, which they usually don't. Usually, they're happy to let me charge, and are very curious about the car. You can also tell them that the electricity you're consuming amounts to maybe $1 per hour because that's all a 240v/50a circuit can put out (depends on the rate they pay for electricity, but even at residential rates it's typically just over $1/hour); so they're not losing any money on the deal.

Some campgrounds don't have hosts/managers; there's just a dropbox with envelopes for paying the overnight fee. I just put some money in the envelope and write a note on the back explaining that I was there for an hour and the money for it is inside the envelope, and then include my name and phone number (no one has ever called me).

I generally have better luck with private campgrounds than state parks. State parks can't do anything without a state policy--that's the way it should be. But private places can do whatever the owner wants, and so they don't have to have a policy on the matter.

Yes, all you need is your Telsa charger with the NEMA-1450 adapter on it. Good luck.

There is a RV park right off of I44 at Marshfield, Mo. about 15 miles or so from Springfield. I believe it is called RV Express 66. They have a drop box at the front that they said I could leave $5 or $10 depending on how much you charge. They have 50 amp plugs. Just bring your normal cord. Make sure the breaker doesn't trip if you charge at 40 amps, I have had this happen a time or two. You can change stalls or dial it down a little. It is 30 miles from there to my house and in the winter from St. Louis, in a S85 I stopped because it was going to be close. I have a S85D now and it makes it easily all the way home (221 miles). I haven't taken it in the winter yet though. There is also a Green Stay Inn at Chestnut and 65 in Springfield that has 2 tesla chargers. They are wired at 40 amps not the full 80. Unless you have dual chargers it doesn't matter.

I typically call ahead to the RV Park, and mention that I have an EV, and that I will be needing a charge.
And could they please assist me in allowing me to charge at their location.
When I tell them I will be charging the car and need a 50 amp outlet, most of the time they are okay with it.
A little humility, some flexibility and a sense of humor go a long way toward negotiating a successful charging experience.
But, I have been denied access to an RV Park twice, due to ownership thinking that the car would harm their electrical system.
So it never hurts to have a back-up plan. Or two.

State Parks are typically viable alternative charging spots also.
I suggest paying about $10 for a long charge, and they are typically happy with that amount.

One thing that has not been mentioned: if you are charging at a 14/50 outlet and it is warm/hot outside, if you can be in the shade, you will be less likely to trip the fuse.
Sometimes when you are charging @ 40 Amps, and it is hot and in full noonday sun, it may trip the fuse on the head of the 14-50 plug (safety device).
Then you are limited to 30 Amps (slower) charging rate.

It does pay to watch the charge rate while the car is initially charging @ a 14/50, because sometimes the electrical outlets/systems are not in premium condition.
So you might need to relocate to another location in the RV Park or Park.
At one RV Park I once was charging @ about 23 miles per hour at several different bays, so I figured that they must have had a 208V system in lieu of a 240 V system.

If you need a list of RV Parks for that route, PM me, and I will forward them to you.