In my part of California, Park Rangers are prominently armed and they carry themselves that way, too.
A little short of a frowny scowl, but not by much.
When I was a kid they were nice and many of them had no guns. They’d give you pointers about the safety of your fire, and in some cases they’d collect your camp site fee.
I don't think they're armed in Philly. They simply help guide tourists, I believe, and some lead tours at the historical sites. That's all I've ever witnessed them doing, anyway.