"Japanese attacks on U.S. mainland. A Japanese sub fired on a oil refinery in Santa Barbara California on Feb. 23 1942. Also a Japanese float plane dropped incendiary bombs on U.S. forests in Oregon on Sept 9th and 10th ( 2 missions)"
http://www.answers.com/Q/What_date_was_a_Japanese_submarine_sighted_off_the_California_coast_in_World_War_2