M For Missoula - Mount Sentinel, Missoula, Montana

When you stand just below it, Mount Sentinel's "M" really is rather gigantic - I inched back down the trail until it mostly fit in my viewfinder. And you don't fully appreciate the annoyingly arduous trail until you turn through that 11th switchback to arrive at the M (which is not the same as "at the top" - you can go further up and further in, and even explore an old mine cave - hence the trees visible between M and sky!)