Final answer:
The expansion of the city in outlying areas located at the greatest distance from the city center was led by expanded railway networks.
Step-by-step explanation:
The aspect of transportation that led to the expansion of the city in outlying areas located at the greatest distance from the city center was expanded railway networks. The invention of the electric streetcar in 1888 allowed cities to increase in size, as people could live farther from their place of employment as long as they were within walking distance of a streetcar line. Streetcar suburbs grew along these lines, connecting the city center to the outskirts.
These suburbs were often segregated by ethnicity and race, and they offered single-family homes with access to amenities like parks, plumbing, and electricity. The convenience and ease of using the railway networks attracted people to move further away from the city center and contributed to the expansion of the city in outlying areas.