Which invention was essential in electrifying American cities during the Gilded Age?

The electric light bulb played a pivotal role in electrifying American cities during the Gilded Age. Invented primarily by Thomas Edison and refined through contributions from others, the light bulb transformed street lighting, enabling cities to extend activities into the evening and significantly enhancing public safety. Its adoption marked a shift from gas lamps to electric lighting, leading to a revolution in how urban spaces were illuminated, allowing for not just safer streets but also longer working hours for factories and the growth of nightlife in cities. This widespread adoption of electric lighting was a key factor in the broader modernization that characterized the Gilded Age, significantly impacting industrial operations, urban development, and even everyday life. Other options, such as the phonograph, television, and radio, while influential in their own right, did not have the same direct and immediate impact on the electrification and transformation of American cities during this period.