Telephone & Light Patent Drawings Background In 1876 Americans held a Centennial Exhibition in Philadelphia to celebrate the nation's birth 100 years earlier. It was the first world's fair to be held in the United States, and it announced for all to see that the nation had come of age as an industrial power. Over 8 million Americans attended, many traveling the railways that now spanned the continent. Of all the exhibition buildings, Machinery Hall drew the most admiration and wonder. Its displa