<P> The first transmission of three - phase alternating current using high voltage took place in 1891 during the international electricity exhibition in Frankfurt . A 15 kV transmission line connected Lauffen on the Neckar and Frankfurt am Main, on a 175 km long distance . </P> <P> Initially transmission lines were supported by porcelain pin - and - sleeve insulators similar to those used for telegraphs and telephone lines . However, these had a practical limit of 40 kV . In 1907, the invention of the disc insulator by Harold W. Buck of the Niagara Falls Power Corporation and Edward M. Hewlett of General Electric allowed practical insulators of any length to be constructed for higher voltages . </P> <P> The first large scale hydroelectric generators in the USA were installed in 1895 at Niagara Falls and provided electricity to Buffalo, New York via power transmission lines . A statue of Nikola Tesla stands at Niagara Falls today in tribute to his contributions . </P> <P> Voltages used for electric power transmission increased throughout the 20th century . The first "high voltage" AC power station, rated 4 - MW 10 - kV 85 - Hz, was put into service in 1889 by Sebastian Ziani de Ferranti at Deptford, London . The first electric power transmission line in North America operated at 4000 V. It went online on June 3, 1889, with the lines between the generating station at Willamette Falls in Oregon City, Oregon, and Chapman Square in downtown Portland, Oregon stretching about 13 miles . By 1914 fifty - five transmission systems operating at more than 70,000 V were in service, and the highest voltage then used was 150 kV . The first three - phase alternating current power transmission at 110 kV took place in 1907 between Croton and Grand Rapids, Michigan . Voltages of 100 kV and more were not established technology until around 5 years later, with for example the first 110 kV line in Europe between Lauchhammer and Riesa, Germany in 1912 . </P>

Where had electricity been put to use in the united states at the beginning of the twentieth century