The K-class submarines were a class of eight submarines of the United States Navy, serving between 1914 and 1923, including World War I. They were designed by Electric Boat and were built by other yards under subcontracts. K-1, K-2, K-5, and K-6 were built by Fore River Shipyard in Quincy, Massachusetts, K-3, K-7, and K-8 by Union Iron Works in San Francisco, and K-4 by The Moran Company in Seattle, Washington. All were decommissioned in 1923 and scrapped in 1931 to comply with the limits of the London Naval Treaty.

The E-class submarines were a class of two United States Navy submarines, built by the Fore River Shipbuilding Company of Quincy, Massachusetts, under a subcontract from the Electric Boat Company. They were used as coastal and harbor defense submarines prior to World War I. When hostilities broke out, the E class were mostly used as training boats; however, E-1 operated on war patrols based in the Azores. During this time, the need for an improved permanent bridge structure was discovered; the temporary piping-and-canvas bridges were inadequate in the North Atlantic.