French's 65 foot tall statue dwarfed every other sculpture at the Fair. And, while the 24 foot tall replica (dedicated in 1918) that stands at the former site of the Administration Building in Jackson Park provides an admirable glimpse of the original's majesty, it doesn't really provide a good reference to scale. So, think about this. The famous Chicago Picasso standing in Daley Plaza is 50 feet tall; 15 feet shorter than Mary. But, a picture is worth - well, you know...so...
(From: The World's Columbian Exposition: The Chicago World's Fair of 1893 by Norman Bolotin & Christine Laing, University of Illinois Press, 2002.)
So, why is the Statue of the Republic often referred to as "Big Mary?" I honestly don't know for sure, but I suspect it is in reference to "Marianne," the national emblem of France.
The Statue of the Republic
ENGIRT with dreamful beauty thou didst stand,
By day and night illumined, and to thy feet
The gathered nations thronged with homage sweet —
The world's hope shining in thine outstretched hand.
The nations left thee there upon the strand
To isolation splendid and complete;
The flames rose round thee with their withering heat,
And touched thy flashing beauty to a brand.
Yet still unscathed thy spirit could not die;
And o'er the land thy rising genius leads
And summons all to freedom and the sky.
Like thine own eagle that no respite needs
But sunward mounts with ever clearer eye,
Thou dost persuade to high and higher deeds.
Horace Spencer Fiske
From: Ballads of Peace and War (1918)
The Gilded Lady of Jackson Park (Lee Bey)
Daniel Chester French
Brooklyn Museum: Collections: Libraries and Archives: Chicago World's Columbian Exposition
Photo credits: The Republic in Jackson Park, Chicago, IL, USA; J. Crocker, photographer