ADALBERTO ROQUE/AFP/GETTY
Steam Power
Scottish instrument maker James Watt patented the steam engine in 1769, and by 1804, England's Richard Trevithick had built the first working steam locomotive. In the U.S., Pennsylvania native Robert Fulton soon made the steamboat a commercial success, which proved vital to trade along the Mississippi River. Steam-powered trains helped unite the U.S. upon the 1869 completion of the First Transcontinental Railroad.
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