At the age of fifteen, he was sent to college but within the year he ran away to join the filibuster of General William Walker, to Nicaragua but his party was intercepted by American officials.

[1] In 1861, he joined in a conspiracy to seize San Francisco and create a "Pacific Republic" in California and Oregon, but the movement failed because of the loyalty and precautions of Colonel (Brevet Brigadier General) Albert Sidney Johnston.

A few months later, President Lincoln issued an amnesty proclamation granting full pardon to all political prisoners upon the condition that they take and keep the oath of allegiance.

Marc Hamilton played Harpending in the 1955 episode "A Killing in Diamonds" of the syndicated western television series Death Valley Days.

Vaughn Taylor played Harpending in a 1965 episode "Raid on the San Francisco Mint" of Death Valley Days which was hosted by Ronald W. Reagan who was cast in the starring role of banker William Chapman Ralston, the founder of the Bank of California.