Assigned to the Hawaiian Detachment in October 1939, "Astoria" changed home ports from San Pedro to Pearl Harbor. The following spring, she participated in Fleet Problem XXI, the last of those major annual exercises that brought the entire United States Fleet together to be conducted before World War II engulfed the United States. The maneuvers took place in Hawaiian waters, and, instead of returning to the west coast at their conclusion, the bulk of the fleet joined "Astoria" and the Hawaiian Detachment in making Pearl Harbor its base of operations.