I usually ask everywhere. Earlier that morning we were at the Lake Hotel and it was listed on PlugShare as a place that had charging. The man behind the desk drew me a map of where to drive a few hundred yards away where I could plug in. "So I can just plug in?" I asked. He said "Just go ahead and plug in."Anywhere and everywhere, always ask first.
At the Old Faithful Visitor's Center we asked the ranger at the counter where we could charge an EV since PlugShare said that there was something nearby. He said there was charging round the Snow Lodge. I must have driven around the Snow Lodge three times and asked two people where I could plug in to charge an EV. No one seemed to know. Internet connectivity is very spotty everywhere in Yellowstone so it's difficult to navigate and to check apps like PlugShare. (I later found out that the outlets that are used for charging are at another outbuilding that's like dorm for employees.) I drove across the way to the Post Office and spotted the receptacle that I ultimately charged at. I thought (wrongly) "Aha, there it is--that must be it." After my experience at the Lake Hotel a few hours earlier, I thought (wrongly) "I'll just plug in just like before." Bad idea!