As noted in the other answer, the marvel of the electric lights that illuminated the Chicago World's Fair at night are described in some detail. We learn that electric lights "laced every building and walkway" and were the first large-scale test of alternating current. Larson offers another factoid as well: the fair used three times as much electricity as the entire city of Chicago. Of course, as we learn earlier in the book, Chicago at this time is still very much illuminated by gas lights, although electricity has been introduced to the city.
Larson talks about how safe people felt walking around at night in the bright illumination of electric lights and about the beauty of a fountain's water lit by electricity.
As for a specific historic reference, Larson quotes a Polish immigrant girl named Hilda Satts who attended the fair with her father. She was only formerly familiar with kerosene lights. Larsen quotes her saying that, in contrast to kerosene, the electric illumination is "like getting a sudden vision of heaven."
She is also surprised that the electric lights are turned on by a switch and do not require matches.