Is this a real thing?

To an extent-yes. Reenacting is a pretty big thing, in the east especially, with sites like Gettysburg doing massive battles. I don't know for sure about something like a trek happening, most stay stationary, and I don't know if one about Louis and Clark even exists. But,at most reenactments people do were full period garb a try to live with only period actuate things...when the public is around. As most reenactments have a battle and some Q&A seasons with the actors, there is normally a public, but after the public leaves for the night it's pretty normal to see someone dressed in full garb on twitter. So, in short: people do pretend to be like another person, but only when preforming or talking to the public. (woah, sorry this is so long, I just really like this thing, hope this helped!)