Japanese submarine sighted in Alaskan waters according to the U.S. Joint Intelligence Committee. Daily summary dated 23 February 1942

An item reported that in the noon of 22 February an enemy submarine was sighted on a distance of 17 miles north east of Chernofski, Unalaska Island, Alaska. On 21 February was she also seen. The J.I.C. commented that the  Japanese seemed to be continuously patrolling in that area to prevent a surprise attack on Japan with Alaska as starting point. The proof was that despite the frequently reported submarines none ships were attacked in the same area.

Source

Map Room Papers (Roosevelt Administration), 1942 - 1945. MR0423. U.S. Joint Intelligence Committee. Daily summary No. 75 dated 23 February 1942