A riparian species, cottonwoods are a conspicuous indicator of water at or near the surface of the ground where they occur in the desert.
[3]: 284 The diversion of the Southern Emigrant Trail and the later stage road south of the Mexican Border was due to the Algodones Dunes, extensive sand dunes located west of Fort Yuma and northwest for over 50 miles that were impassable to wheeled vehicles of the era.
The route followed the Colorado River south from Fort Yuma to beyond Pilot Knob where it turned west.
In years of extraordinary flooding or if the Colorado changed course down these channels it might flow north, to the Salton Sink.
[3]: 289–292 In a report on his march to Fort Yuma in October, 1861, Lieutenant Colonel Joseph R. West, marched east along the mail route describes Alamo Mocho on October 31, six months after the stage line abandoned the route: Agricultural development and the canalizing of the Colorado and Alamo River waters, during the twentieth century in Mexico, have completely obscured the site of the station.