The Chicago Transit Authority (CTA) logo is displayed beneath the steel elevated tracks that define the Loop, the city’s central business district. The structure, part of the “L” system first built in the late 19th century, remains one of Chicago’s most enduring symbols of urban mobility. Overhead girders and riveted beams—many still original to the early 1900s—carry trains above streets lined with early skyscrapers and historic facades. The CTA continues to operate one of the largest and oldest public transit networks in the United States, moving more than a million riders daily through Chicago’s interconnected system of rail and bus lines.