The first-come arrival playbook
2,080 of the 5,569 federal campgrounds in this atlas never take a reservation; the live list is on the first-come page. No booking window, no release morning, no six-months-ago version of you who guessed wrong about the weather. The whole game is showing up at the right hour of the right day with the right things in the truck.
When sites turn over
Checkout at most federal campgrounds is noon, posted on the entrance board. Some say 11 a.m., a few say 2 p.m. Campers who are leaving mostly leave between mid-morning coffee and the deadline, so arrive between 10 a.m. and noon and you can watch it happen: a rig pulls out, you pull in behind it. Arrive at 4 p.m. and you inherit whatever the morning people passed over.
Earlier is not better. At 8 a.m. the campground is full of people eating breakfast who won't leave for three hours, and you can't tell the leavers from the stayers.
Which day you arrive
Sunday through Thursday, a first-come campground is a different institution than the same campground on Friday. Midweek in most national forests you can roll in at 2 p.m. and pick among open sites. Friday, the math inverts: at popular forests within two hours of a city, sites go by early afternoon, and the loops near a trailhead or a swimming hole can be done by 10 a.m. Holiday Fridays, done by Thursday.
The veteran move is arriving Thursday night. Claim the site, pay through Sunday, and Friday afternoon becomes someone else's problem.
Claiming a site
A paid tag on the post means taken, even when the site is bare. People pay for two nights and spend all day at a trailhead. Read the post before you unpack anything.
To claim an open site, occupy it and then pay, in that order and quickly. A camp chair and a cooler on the table hold it for the ten minutes it takes to walk back to the fee station, and the stub you clip to the post is the real claim; gear alone is a suggestion that hosts and rangers are free to ignore. Don't take two sites while your group makes up its mind, and don't hold one for friends arriving tomorrow. Every host has a story about that, and you don't want to be in it.
Arriving after dark
It happens. Drive the loop slowly with your headlights low, take an untagged site as quietly as you can manage, and pay before you do anything else, because "we'll pay in the morning" is exactly what a host hears from people who never do. Skip the campfire, skip the elaborate dinner, apologize with your behavior to the neighbors you woke. Popular first-come campgrounds are picked over by dark on a summer Friday, which is most of why the Thursday-night move exists.
The iron ranger
Most first-come campgrounds collect fees through an iron ranger, a steel pipe with a slot, and it makes no change. Bring cash in small bills: a $24 stay paid with two twenties is a $16 donation. Take an envelope from the fee station, write the site number, dates, and license plate on the front, put the cash in, drop it in the pipe, clip the stub to the post. A growing share of campgrounds also post Recreation.gov's Scan & Pay code at the fee board, which works exactly until your phone loses signal. Carry the cash anyway.
Interagency Senior and Access passes cut the nightly fee at many Forest Service and BLM campgrounds, commonly by half; the envelope has a line for the pass number.
The backup plan
Pick two alternates before you leave cell coverage, both within about thirty minutes of the target, and screenshot their locations from the map. A backup chosen at your kitchen table beats one improvised at 6 p.m. with a hungry car. If everything is full, dispersed camping along forest roads is legal in most national forests and free; the rules and the caveats are in the free-camping guide.
One more thing about the envelope: it asks for your plate number. Know it, or you'll be the one walking back to the car with a headlamp.