Louisiana is entirely on a district/regional/state system for outdoors. Nothing during the regular season matters. This year there are seven separate classes based on school, but next year they're going down to six. There are a few slight qualifying differences for some of the smallest classes, but this is how it generally works:
District: max two individual entries in each event per school. Most districts are 6-8 teams, I think the smallest districts have 5 teams and the biggest have 10. Top four individuals (and top four relay teams) from each event go to regionals.
Regionals: Each class has three regions. Most regions have three districts, but a few have four. So typically each individual event will have 12 competitors, sometimes 16. Top three qualify to state.
State: nine entries in each event. No prelims for anything, just finals. All events for a given class take place in one day.
Some of the districts are very uneven in terms of quality. One district has a 12:34 girl missing out on regionals while another girl will make it to regionals with an 18:41 (and get lapped multiple times by girls who have broken 10:50). But the regions are a little more balanced. I understand the impulse to see better competitors make it to state, but if you're #5 in your district or #4 in your region you probably wouldn't make the podium at state.
Frankly, I much prefer it this way to a time-based system. We have that for indoor, with all five qualifying meets either at LSU or McNeese. Those regular season meets usually end up being miserable all-day experiences, with endless heats of the 400 and various other sprints. I have zero interest in attending a meet like that (I'm a HS teacher and XC coach, but I don't coach track). Nor do I want to sit through some outdoor invitational meet where a bunch of people are just out there chasing times.
But a district meet against our biggest rivals, or regionals with spots on the line for state, or a state championship meet? That's something interesting to me as a fan. It's like rojo always says, we don't need more meets, we need more meets that matter. High-stakes, win-or-go-home action is good viewing. Not, "Oh, little Suzy had a bad day, but her time from earlier this year might get her in, so we just have to sit around and wait for all the other district meets to end." Top four get to regionals, top 3 get to state. That's easy to understand and fun to watch.
I get that a system with some at-large spots might make sense for some states, where the quality can be extremely uneven. There was some talk of trying to go to a time-based system in Louisiana, but the track coaches weren't too interested. I just think it adds too many complications in terms of certifying all the regular season meets, making sure everyone has working wind gauges, etc. I also think it would unfairly reward the richer schools that can afford to go to more meets to chase times.