I find Washington County in three of my sources, but all three show it as a bluegrass variation, by Kenny Baker, based on Washington and Lee Swing.

About the only similarity between the three is that they're all three notated for fiddle in A Major.

Is this the right song?

If so, you might be able to find it faster than I could get it posted -

Fiddler's Fakebook, Oak Publications, Washington County p285

Craig Duncan Master Fiddle Solo Collection, Mel Bay, Washington County p135

Phillips Collection of Trad. Am. Fiddle Tunes, Vol 2, Washington & Lee Swing (B) aka Washington County p163.

I can't connect this title to anything by Guthrie, although my sources only include a couple of collections of his songs.

John