There is a Red River Valley in Texas. It might have become transplanted by cowboys there.
There's a verse about the "wild chapparal" (not sure how to spell it) but refers to desert-like
plants I think. I would go with the Iowa reference but here's the old problem,
when it first appears in print is not the definitive source of a song's beginnings.

It might even have been an old hymn. It has that kind of a cadence. If you put it
into a six-eight/two-four feel it could go like that.

A song travels far and wide. "The cowboy that loved you so true" shows the Texas
connection.

If it's a real folk song, you may never know the source.

Frank Hamilton