The document discusses key events and developments in the United States as it emerged as a world power in the late 19th century. It describes the construction of the transcontinental railroad which connected the country coast to coast, fueling western expansion. It also discusses the discovery of silver in Nevada and the major oil find at Spindletop, Texas, which transformed the country's energy industry. Finally, it summarizes the deadly 1911 Triangle Shirtwaist Factory fire in New York City which killed 146 garment workers and led to new labor laws and safety regulations.