It sounds unbelievable—but Arizona once mobilized troops and launched a “navy” in a standoff with California. We revisit the Parker Dam and the bizarre battle for control of the Colorado River.

PARKER, Arizona—South of Headgate Rock Dam, beyond riverbanks lined with willow and mesquite, the broad floodplain of the Colorado River spreads across emerald fields and sun-bleached earth.

Arizona was girding for war with California over the Colorado River. The year was 1934 and the place was the construction site of Parker Dam, downstream from the nearly completed Hoover Dam.