Having become fully disgruntled with the inadequacies of the political structure and state and federal governments of the United States, Norton took matters into his own hands on September 17, 1859, when, in letters to the various newspapers of the area, he summarily proclaimed himself "Emperor of These United States":

At the pre-emptory request of a large majority of the citizens of these United States, I Joshua Norton, formerly of Algoa Bay, Cape of Good Hope, and now for the last nine years and ten months past of San Francisco, California, declare and proclaim myself the Emperor of These United States.

...

For all of his quirks and regardless of the precise nature of his psychological condition, it cannot be denied that Emperor Norton I was, on some occasions, a visionary, and a number of his Imperial Decrees exhibited a profound wisdom. Among his many edicts were instructions to form a League of Nations, and he explicitly forbade any form of discord or conflict between religions or their sects. The Emperor also saw fit on a number of occasions to decree the construction of a suspension bridge connecting Oakland and San Francisco...

It was during one of his Imperial inspections that Norton is reputed to have performed one of his most famous acts. During the 1860s and 1870s there were an unpleasant number of anti-Chinese demonstrations in the poorer districts of San Francisco, and ugly and fatal riots broke out on more than a handful of occasions. During one such incident, Emperor Norton I is alleged to have positioned himself between the rioters and their Chinese targets, and with a bowed head began to recite the Lord's Prayer repeatedly. Shamed, the rioters dispersed without incident.

A scandal occurred in 1867 when a police officer named Armand Barbier arrested the Imperial Majesty, for the purpose of committing him to involuntary treatment for a mental disorder. This caused monumental outrage amongst the citizens of San Francisco and sparked a number of scathing editorials in the newspapers. Police Chief Patrick Crowley speedily rectified matters by ordering the Emperor released and issuing a formal apology on behalf of the Police Force. Emperor Norton I was magnanimous enough to grant an Imperial Pardon to the errant young police officer who had committed the (perceived) act of treason. Possibly as a result of this scandal, all police officers of San Francisco thereafter would salute the Emperor as he passed in the street.

...

Emperor Norton I was clearly much loved and revered by his subjects. Although penniless, he regularly frequented the finest restaurants in San Francisco, and the proprietors of these establishments took it upon themselves to add brass plaques in their entrances that declared "By Appointment to his Imperial Majesty, Emperor Norton I of the United States".

...

Emperor Norton I did receive some small tokens of formal recognition for his station; the census of 1870 records a Joshua Norton residing at 624 Commercial St, and lists him with the occupation of "Emperor". The Emperor would also issue his own money on occasion in order to pay for certain debts, and this was an effective local currency, generally accepted as legal tender by San Francisco businesses.

...

The benevolent and largely harmless reign of Emperor Norton I came to an end on the evening of January 8, 1880, when he collapsed on the corner of California and Dupont (now Grant) streets while on his way to a lecture at the Academy of Sciences. His collapse was immediately noticed by another citizen who raised the alarm, and, according to one newspaper, "the police officer on the beat hastened for a carriage to convey him to the City Receiving Hospital". The Emperor passed away before the carriage could arrive.

The following day the San Francisco Chronicle published an obituary on its front page under the headline "Le Roi est Mort" ("the King is Dead"). With a tone tinged with sadness, the article respectfully reported that "On the reeking pavement, in the darkness of a moonless night under the dripping rain..., Norton I, by the grace of God, Emperor of the United States and Protector of Mexico, departed this life".