We actually had to walk maybe half a mile from the closest place we could drive, at Mojave Greenway Road (which doesn't show up on Google), approximately the yellow marker on this map, i think, because past there Border Monument Road is a private road (lots of no trespassing and neighborhood watch signs, etc), but it's BLM riparian conservation area land on the east side of that road so we just walked across a field to the river and then down the river.
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