His birth name was Jacob Johnson. Emigrating from his native Sweden, Swanson volunteered for service in the United States. Navy and was assigned to the Union brig United States Ship (1861). His enlistment is credited to the state of Massachusetts.
On January 15, 1865, the North Carolina Confederate stronghold of Fort Fisher was taken by a combined Union storming party of sailors, marines, and soldiers under the command of Admiral David Dixon Porter and General Alfred Terry.