 Clad in gray Indiana limestone, topped with a copper pyramid roof, and standing on a site running east–west on Jackson Boulevard and north–south on LaSalle Street, the tall art deco-styled building opened on June 9, 1930.It serves as the southern border for the skyscrapers hugging LaSalle Street and is taller than surrounding structures for several blocks.The Chicago Board of Trade has operated continuously on its fourth floor since the 1930 opening, dedicating to what was then the world's largest trading floor.