Although subways were the choice in other growing cities like New York and London, Chicago selected elevated railways because they were cheaper to construct and did not require much digging (there were concerns at the time that the city's swampy soil might not tolerate a subway system).

Chicago’s transit system, famously known as the "L" (short for "elevated"), is primarily above ground because of the city's unique 19th-century geography and engineering economics. When the first lines were built in the 1890s, Chicago’s soil was notoriously swampy and soft, making deep tunneling incredibly expensive and technically dangerous compared to other cities. Building iron and steel structures over existing alleys was a much faster and cheaper way to expand transit without disturbing the already crowded street-level traffic. This created the iconic "Loop" that defines the city's downtown skyline today. While there are underground "subway" sections (specifically for the Red and Blue lines through the city center), approximately 70% of the rail system remains elevated. In 2026, the "L" is not just a utility but a cultural landmark, offering passengers a "living tour" of Chicago’s diverse architecture and neighborhoods, a perspective that is entirely lost in the dark, subterranean tunnels of cities like New York or London.