Answer: Tacoma
Unlike later pre-war carriers, Lexington (along with her sister Saratoga), was not equipped with a standard steam turbine propulsion system, but was instead fitted with what was described as a "turbo-electric" system - steam from the boilers was used to provide power to four generators that generated electricity. This was then used to power a pair of electric motors located on each of the ship's four propeller shafts, making the propulsion system ostensibly a massive electric generating station.
In late 1929, a drought in the west of Washington led to Lake Cushman receding. The lake provided water for Cushman Dam No. 1, a hydro-electric plant that was the primary source of power for the city of Tacoma. Once the water level receded below the dam's intakes, the city's electrical supply was significantly reduced, which led to the city requesting help from the federal government. The government's response was to send Lexington, which had been at the nearby Puget Sound Naval Shipyard in Bremerton, to Tacoma, and rig up lines from the ship's electrical generating system into the city power grid. Lexington remained hooked up from 17 December 1929 to 16 January 1930, by which time rain and snow-melt had raised the water levels in Lake Cushman.