There was a sign many years ago but it has long since come down. 'Sorry to be a little elusive but no good could come from pinpointing this tiny, shallow, private pond.
@fishtales - I've done the same thing. There are many farm ponds in the valley, most all of which require permission, sometimes written, to access them. Ask your friends and neighbors. I have networked access several times in the past.
Most importantly, if you pack it in, pack it out. Make it a goal to leave the area cleaner than you found it. The alternative is losing access forever. I've seen it happen too many times.
I was born in McMinnville and it was was my home town until recently (now in Tualatin due to business) so I'm familiar with the area.