All of it gone
The record says all of the main buildings were demolished.
The questionAre there foundation remains under Kountze Park, and has anyone dug for them?
Investigate · Omaha 1898
Agricultural Building, Trans-Mississippi Exposition of 1898 in Omaha, Nebraska - DPLA - 813666d28eb40723fe32040a84afc13d
1 clue in this photo
Photo: Key, John Ross, 1832-1920; L. Prang & Co · Public domain · via Wikimedia Commons
Same kind of clue, elsewhere
#6A steel cage under an intact domeIf grand civic buildings had steel and brick cores, what did the fair palaces have inside?
1,500 buildings, almost none leftWhere did all that material go?
Danvers 2006: a crane to bring it downIf taking it down needed modern machinery, how was it built with horses?
A Euston Arch column from a canalWhere else did demolished stone end up, and what was taken out of the record?
Boston 1872: shells of stoneWhat did the fires clear, and what was put back?