In the 40 years we've been camping, we had only one theft (from our vacant tent) and have only felt in danger one time (We left at sunrise, instead of staying three days.).
There's no human way you can be 100% protected, but you can and should "follow your gut feeling." We checked out a campground near the river in Memphis, TN. It was listed as OK, in the camping directories. To get there, we passed an abandoned motel that had been vandalized and gutted; the neighborhood had seen better days. Did we stay there? Fat chance!
We always check this forum, ask others, and - starting this year - are looking for "Family RV Parks," "Camping Resorts," etc. We also ask about security, ask where the Host stays, and if there is a 24-hr. emergency number to call. Then - we enjoy ourselves!
We've found that most RVers soon get to know those around them, and we all try to take care of each other - so everyone enjoys the experience. That's what good neighbors do!
