
Nikola Tesla's alternating current technology could transmit power efficiently over great distances, eliminating the need for a power station every mile or so down the road. The 1895 debut of Tesla's George Westinghouse-financed Niagara Falls alternating current hydroelectric plant irrevocably demonstrated AC power's practical superiority, and every major consumer electrical utility initiative since has been based around an alternating current infrastructure.
That doesn't mean DC power went away overnight. There were still many vested interests in the DC power industry, and many customers already had DC power appliances and lighting they weren't eager to replace. Thus, many New York residences and businesses remained on DC power decades after AC power became the norm. But the actual longevity of consumer DC power in New York is still startling.
In what year did the last of New York's DC electrical power customers to convert to AC service?