It has always been my my understanding that "an" should precede "historical" and "a" before "historic".
The California Gold rush of 1849.
Historic Folsom was created in 2005.
because he was famouse
It can be either, as "a historic" works better for a "hard H" (as in hit), while "an historic" is used where the H is soft or not pronounced (as in some British pronunciations). While "a historic" is more commonly used, it is possible to drop the H entirely (saying, in effect, 'anistoric') and be understood.
Three antonyms for the word "historic" are; insignificant, unimportant, and unremarkable.
It is "a historic event"
i was raised by wolves
u were born
who was in that event
golden golden
The Storming of the Bastille
The Crusades
America became a country.
Probably the royal wedding.
when there is a state of crisis
The Alamo
battle of the alamo