His wife's family was wary of Derby because his erratic, flippant manner infuriated his superiors.
Coons tricked Derby into marrying her by placing a notice in the San Francisco paper stating that she would depart with her mother back home to St. Louis, Missouri, although she had no intention to do so.
While waiting for approval of his San Diego River diversion plans, he had some time on his hands.
When another writer started writing articles with his pen name Squibob in a competing San Francisco newspaper, Derby wrote an article "killing off" Squibob and continued to write with a new pen name, John Phoenix.
In 1857 Derby had amaurosis (today, some historians think he had a brain tumor), which prevented him from reading or writing.
He requested leave from the Topographical Engineers in 1859 and moved to New York, where he died shortly after the start of the American Civil War.