The White Post (as promised)

I drive past this white post four times a day. This white post is located, coincidentally enough, in White Post. (hence the name) I was told at one point that Lord Fairfax (or Washington, depending on who you ask) put this white post here to mark a boundary. I tried to look up its historic significance online, but I get quickly frustrated/ bored looking stuff up online. So instead of a history lesson, my fellow blippers get my guesses.