If you are younger than 55, you can still stay at an RV park that advertises itself as "55+." You don't really need to be 55 or older.
A federal law says that if a park wants to call itself 55+ it must not rent more than 20 percent of its spaces to people younger than 55. So should someone show up younger than that, the park management can accept them, provided the park is still below the 20 percent "young people" occupancy limit. But they have the right to turn them away if they choose.
"We're a don't tell, don't ask park," one 55+ park owner told me, which was her way of saying "we can take anybody." But what she did not say is that the main reason a park would turn away people younger than 55 would be if they had kids along.
Their residenets don't want kids around. They don't want them riding their bikes, screaming or otherwise making noise. "These snowbirds would rather be around snakes than kids," a friend in the RV industry told me.
So instead of advertising "no kids" on its sign, a park says "55+."
You find these parks mostly in snowbird areas like Arizona. You seldom see them elsewhere.
When I was younger I once got turned away at a 55+ park. I was probably around 40. I didn't have any kids with me. But I did have an old, ugly motorhome, so maybe that was the reason. Whatever the case, I was not allowed to stay and that made me mad.