WAR OF CURRENTS

Thomas Edison, American inventor and
businessman, known as "The Wizard of
Menlo Park", pushed for the development
of a DC power network.
In the "War of Currents" era (sometimes,
"War of the Currents" or "Battle of
Currents" ) in the late 1880s, George
Westinghouse and Thomas Edison became
adversaries due to Edison's promotion of
direct current (DC) for electric power
distribution over alternating current (AC)
advocated by several European
companies [1] and Westinghouse Electric
based in Pittsburgh, Pennsylvania, which
had acquired many of the patents by
Nikola Tesla .
The direct-current system generated and
distributed electric power at the same
voltage as used by the customer's lamps
and motors. This had the effect of large,
costly, distribution wires and forced
generating plants to be near the loads.
With the development of a practical
transformer, power could be sent long
distances over relatively small wires at a
convenient high voltage, then stepped
down to the voltage used by a customer.
Alternating current generating stations
could be larger, cheaper to operate, and
the distribution wires were relatively less
costly. As the competing systems were
protected by patents, there was
commercial rivalry between the
Westinghouse and Edison companies. A
publicity campaign by Edison highlighted
the safety issues of high voltage
transmission.
The lower cost of AC power distribution
prevailed, though DC systems persisted
in some urban areas throughout the 20th
century.

Know more...
  http://en.m.wikipedia.org/wiki/War_of_Currents