War of Currents

Tesla's alternating current work put him firmly on the "AC" side of the so-called "War of Currents," an electrical standards battle waged between Thomas Edison and George Westinghouse. Tesla's patents, along with the others that Westinghouse's company had acquired or developed, allowed Westinghouse to build a rival AC system that could compete with Thomas Edison's DC system.

In 1893, George Westinghouse won the bid to electrify the 1893 World's Columbian Exposition in Chicago with alternating current, beating out a bid by Edison to electrify the fair with direct current. This World's Fair devoted a building to electrical exhibits. It was a key event in the history of AC power, as Westinghouse demonstrated the safety, reliability, and efficiency of alternating current to the American public. At the Columbian Exposition, Tesla demonstrated a series of electrical effects previously performed throughout America and Europe,:76 included using high-voltage, high-frequency alternating current to light a wireless gas-discharge lamp.:79 An observer noted:

Within the room was suspended two hard-rubber plates covered with tin foil. These were about fifteen feet apart, and served as terminals of the wires leading from the transformers. When the current was turned on, the lamps or tubes, which had no wires connected to them, but lay on a table between the suspended plates, or which might be held in the hand in almost any part of the room, were made luminous. These were the same experiments and the same apparatus shown by Tesla in London about two years previous, "where they produced so much wonder and astonishment".