 A gift from the William Wrigley , Jr . Company , the limestone replica peristyle rises to a height of nearly 40 feet ( 12 @.@ 2 m ) ( one source says the columns were planned to rise to 36 feet ( 11 @.@ 0 m ) ) , restoring a classical elegance to Grant Park . The William Wrigley , Jr . Foundation contributed $ 5 million to the monument , and the entire square , which cost $ 5 million to build , was named in its honor . The Millennium Monument is a tribute to the individual , corporate and foundation benefactors of Millennium Park . The pedestal of the peristyle is inscribed with the names of the 115 financial donors ( including Oprah Winfrey ) who made the 91 contributions of at least $ 1 million each to help pay for Millennium Park . The New York Times describes the pedestal as French marble , but other sources mention the use of French limestone . These 115 donors are referred to as the founders of Millennium Park in official park brochures published by the City of Chicago and distributed at the visitor 's centers as well as in other press accounts . Their contributions not only paid for the construction of the park , but also provide for its ongoing conservation . 
