Before the Columbian Exposition, as Olmsted said, the area in Jackson Park was not
promising, with its boggy swales and sand ridges covered with "vegetable
mold.” J. Francis Murphy made a watercolor sketch of what it looked like just
before work began in January 1891.
Olmsted and Burnham and their partners worked out the grand
scheme of lagoons and waterways and started dredging out the pans and building
up the shores that would hold the massive buildings.

Olmsted decided to keep one of the ridges. He cut off 15
acres and turned it into an island, which he himself called the Wooded Island. He
hoped that he could avoid structures on it because he wanted it to be a restful
oasis among the overwhelming artificiality of the Fair. It wasn’t just an
interesting aesthetic contrast to him. Olmsted believed in the healing power of
nature. He’d heard Emerson in person and read the Transcendentalists, so he saw
the island and Lake Michigan for the spiritual uplift that he wanted the fair
to deliver.
The problem was that the shorelines were raw and staked up from
being sculpted. Olmsted raided the wild riverbanks south of the city,
particularly along the Calumet, for thousands of water-loving shore plants. Olmsted
wasn’t a native plant purist—he needed a lot of plants in a hurry that would
handle the fluctuating water levels of the lagoons. It was a triumph that was
praised in guidebooks and visitor diaries as the most magical part of the
magical city. As one guidebook put it
“This bit of nature dropped down in the midst of the “City
of White Palaces” is the final touch of perfection. Every writer who has told
of the Fair, and every artist who has drawn it, has agreed to this….The visitor
finds in the sedges, rushes, and other semi-aquatic vegetation along the shores
of the Wooded Island and of the mainland of the Lagoon, a great triumph of
unconventional horticulture.”
The old Bur Oaks in the middle provided some shade, which
Olmsted filled in with quick-growing shrubs and trees. He had so little time to
get the effect he wanted. Early photos show that the island looked a bit sparse.
As the summer went on, landscape filled in and earned its
name as the Wooded Island.
During the Fair, a favorite view of artists was of the very
south end of the island, where the Bur Oaks contrasted with the formal Court of
Honor.
And you can walk
among them now. They are still clustered around the bridge at the south end of
the island.
The oaks were old even during the Fair. It became clear how
old in 2003, when the largest oak blew down in a derecho that took out hundreds
of trees on the southside. The 90-foot spread of its crown acted like a sail
and pulled it up out of the sandy soil where it had stood since 1730. Bur Oaks grow
in savannah landscapes, so they stretch out gnarled limbs horizontally. They
also grow in nutrient poor soil, so they grow slowly. You can spot the old ones now (there's also a map of trees in boxes at the bridges.)
With time and abandonment, especially after the Nike Missile
base blocked access to the area, the island became overgrown with invasive species.
In the 2010s, the Great Lakes Ecosystem Restoration came along with the massive
effort to resculpt the shorelines and plant 600,000 native plants and recreate
the ecosystem. As soon as the competition from the invasives was gone, baby Bur
Oaks surprised everyone by sprouting from long buried acorns. When you see a
little sapling in a protective cage, that’s a volunteer Bur Oak insuring the
island will stay Wooded.