In the 1860s Watrous was a US mail agent in San Francisco, where he befriended Bret Harte (see, for instance, Axel Nissen's Bret Harte, Prince and Pauper [Jackson: University Press of Mississippi, 2000], 239.) As such he probably had at least a passing acquaintance with Noah Brooks. He was forced to step down from his position due to his involvement in a vote-buying scandal to elect Timothy Guy Phelps US senator from California (Portland Oregonian, 10 February 1863, 2), and moved to New York, where he went into the lumber business with his brother-in-law. A member of the Union League, he was involved in the purge of the Tweed ring in 1871. In 1891 he returned to San Francisco with a group of capitalists and engineers sent overland to explore the possibility of a canal through Nicaragua, and died as a result of an illness contracted while inspecting the canal site en route (“The Big Canal: One of the Miller Party Talks of It,” San Francisco Chronicle, 19 May 1891, 2).