FCFS Site locations

Technically, all sites are fcfs. Some are the first person to book it on line and some don't have an online option so you show up. I prefer to know I have a site rather than winging it in this stage of the game with sites being hard to snag, especially in a motorhome towing a car. I'd feel the same with a TT. Class B is the only RV type I'd be ok winging it. 

Walmart is FCFS….

Not sure I understand exactly what you are trying to do. If admittedly you run into difficulty when booking sites, how do you think it will be different with fcfs sites which are usually cheaper and likely already full? Add to that, you won't know they're full until you get there and then you're screwed. I feel like the days of loading up the camper with the romance of the open road and no plans are over. Since COVID, camping has exploded and finding sites is difficult enough with plans and booking. Can't imagine the headache of winging it especially with a TT. With a class B you'd probably have more luck urban camping, hotel lots, etc. You might try sites like dyrt, hipcamp, Harvest host, Recreation.gov,  CampsiteTonight, and online forums like Reddit.

Seems like you're just asking if an RVer can travel around these days with no plans/reservations.  We used to do that years ago when we had a small Class C without tow car.  RVing has gotten more popular with both intentional RVers and those without sticks&bricks homes.  But I think you can still do it...IF...you aren't picky about where you camp (first or second choice may not be available), if you stop earlier rather than later in the day, if you don't go near popular tourist sites, and if it is not a holiday.  That said, you might still run into full campgrounds because an RV club happened to book most of the campground for the day(s) you want to stay (happened to us), or people are escaping a wildfire, etc.

There are many websites that list many different kinds of campgrounds...private, city, county, State, Federal...but I have not seen one that specifically lists FCFS campground/sites.  No one website is totally comprehensive.  I have a whole list of websites saved that I use....here are a few:

https://freecampsites.net/

https://uscampgrounds.info/

https://campgrounds.rvlife.com/

https://www.rvparky.com/

You can also search BLM, COE, USFS, etc.

Now our camping style has changed, due to age and disability.  But sometimes, if we are just driving a long way to get someplace (with reservations), I just book each night in the morning before I leave the current campground.

Best of luck!

Gee. Thanks folks for telling me how stupid I am. I actually thought I might get helpful info.

My bad.

In 25+ years of being on the internet, I’m amazed at some of the circular jibberish that people post….

Rvnet is on a retread roll today! 

In 35+ years of camping I’ve never heard of a private enterprise campground that operates on a “First Come First Serve” basis. Why would a business owner want to turn down a sure customer on the chance that maybe someone will drive in? Reservations can often be made even in as little time as a week in advance. Seems much easier to me to make a plan a few months in advance than to try to do something on the fly at the last minute. But maybe I’m just more of the “bird in the hand” type then the “throw the dice and see how they land” type.

Your best bet might be Forest Service boondocking type camping.