… Fortunately, in those days, the good citizens of San Francisco took it as an enormous joke.
“At the peremptory request and desire of a large majority of the citizens of these United States, I, Joshua Norton… declare and proclaim myself Emperor of these United States; and in virtue of the authority thereby in me vested, do hereby order and direct the representatives of the different States of the Union to assemble in Musical Hall, of this city, on the first day of February next, then and there to make such alterations in the existing laws of the Union as may ameliorate the evils under which the country is laboring, and thereby cause confidence to exist, both at home and abroad, in our stability and integrity.”
Norton I, Emperor of the United States
(San Francisco Bulletin, 17th September, 1859)
Here’s his wikipedia entry