The National World War II Museum posted this items about the only Axis attack on the continental U.S. during WWII.
On June 21, 1942 Civil-War era Fort Stevens, near the mouth of the Columbia River in Oregon, was shelled by Japanese forces. The Japanese submarine I-25, with a crew of 97, and armed with a 14 cm deck gun and carrying a seaplane, opened fire. Fort Stevens commander ordered an immediate blackout, and held all fire. This prevented the submarine from accurately targeting the base. Of the seventeen shots, the only damage was to some telephone poles near the base–the remainder landed on a baseball field or a nearby wetland. Just past the battery of Fort Stevens was the northern Kaiser shipyard, which was at that time turning out a Liberty Ship each week.The notion of a submarine carrying an airplane seems a little like science fiction, even today. I believe I have seen the idea in some comic books of the era, but the Japanese deployed such a vessel. The aircraft from I-25 dropped incendiary bombs on the northwest U.S. after the above encounter, but rains and the U.S. Forest Service prevented any noticeable damage.