From the late 1850s, the Pahranagat Valley was a popular place for horse thieves to hide out as they stole stock from Utah and Arizona and made their way to California. Reportedly, at one time there were more than 350 different brands seen at once in the valley and at least one early settler described it as "the toughest place I ever saw." Following the discovery of gold ore in the region and the establishment of Hiko to the north, the thieves were run out of the place.

In 1901, the community of Alamo was laid out by Fred Allen, Mike Botts, Bert Riggs and William Stewart. It was named after the Spanish word for 'poplar' because there were a number of cottonwood trees growing there. Most of its settlers came from Fredonia, Arizona.