[shrubble]

They definitely would be a good place to search. Not only for historical artifacts but becuase the plains would trap the heavier gold flakes that got eroded either locally or upstream.

For instance the state of Pennsylania has no known gold vein deposits but small flakes of gold are often found in the rivers, since the quartz rocks that contained the flakes were eroded, freeing the flakes which are then washed into the river by rain.