UPDATE: Heard from a volunteer at the (very minimally staffed) local
historical society: "The farmer installed a bridge across the ditch
so he could move his machinery across to the adjoining field."

I have my doubts. I'll shoot it again, but I really don't think the
bridge is wide enough or the boards strong enough to support vehicle
traffic. And as of 2005, the farmer didn't own BOTH of the adjoining
sections (though that could have changed). Besides, the bridge is
halfway down the field without a barn or tractor storage shed in
site. Why not access your field closer to the paved road/barn/corner
of field?

He also says the ditch system was installed AFTER the WPA era
(1930s). But that doesn't seem to mesh with the antiquated state and
style of the bridge.

RW