18 U.S.C. § 2151 (Title 18—Chapter 105: Sabotage)
As used in this chapter [18 U.S.C. §§ 2151 et seq.]:
The words "national-defense utilities" include all railroads, railways, electric lines, roads of whatever description, railroad or railway fixture, canal, lock, dam, wharf, pier, dock, bridge, building, structure, engine, machine, mechanical contrivance, car, vehicle, boat, aircraft, airfields, air lanes, and fixtures or appurtenances thereof, or any other means of transportation whatsoever, whereon or whereby such national-defense material, or any troops of the United States, are being or may be transported either within the limits of the United States or upon the high seas or elsewhere; and all air-conditioning systems, dams, reservoirs, aqueducts, water and gas mains and pipes, structures, and buildings, whereby or in connection with which air, water, or gas may be furnished to any national-defense premises or to the Armed Forces of the United States, and all electric light and power, steam or pneumatic power, telephone and telegraph plants, poles, wires, and fixtures and wireless stations, and the buildings connected with the maintenance and operation thereof used to supply air, water, light, heat, power, or facilities of communication to any national-defense premises or to the Armed Forces of the United States.