Center of commerce By Brian Schmidt | June 30, 2021 | Last updated on August 7, 2025 Email Newsletter Get the newest photos, videos, stories, and more from Trains.com brands. Sign-up for email today! Get Updates Center of commerce A Pennsylvania Railroad Geep pulls a string of express cars in front of railroad’s Polk Street freight station near Chicago Union Station. Polk was the country’s largest freight terminal when built in 1918. Ed DeRouin photo Share this article Print Facebook