Rusty Old Wheel

I spotted this rusty old wheel while on a photography trip recently. I don't remember exactly where this picture was taken. It was  in Colorado, on a large ranch belonging to designer Ralph Lauren.

This image speaks of time. A rusty wheel, long discarded, now has plants growing between its spokes. To what kind of thing did this wheel once belong? A wagon? A cart? How long has it been discarded? How old is it?