After complaints from angry alderman, the board voted Thursday to cut that to $16.
The move comes as the museum prepares to open its new modern wing.
Park District spokeswoman Jessica Maxey-Faulkner says the board also cut rates for students and seniors by $2, to $10. And it raised the age at which children will get free admission to 14 from 12.
About the Modern Wing
On Wednesday, the Art Institute invited the media to take a look at the new Modern Wing, which will open to the public on May 16.
The 264,000 square foot Modern Wing addition makes the Art Institute of Chicago the second largest art museum in the U.S.
The sleek, airy architectural wonder is being celebrated worldwide.
"This does allow us to demonstrate to the art world the richness of our collections that have been built by Chicagoans for Chicagoans, not only the collections in the Modern Wing but all the Art Institute of Chicago," said James Cuno, Art Institute director and president.
The Modern Wing was 10 years in the making. It showcases the museum's collection of 20th and 21st Century Art and design, including a vast area for architecture.
"For the first time we've been able to have sufficiently scaled galleries for our architecture," said Cuno.
The building itself adds to the legacy. It's an open, contemporary structure created by renowned architect Renzo Piano, who designed the Pompadeux Center in Paris. He worked with the curators to spotlight the artwork in the city.
"It's about modern art but it's about our collection and its history…and its relationship to the history of the city," said Douglas Druick, Curator, Dept. Medieval to Modern.
The museum will offer free admission to the Modern Wing from May 16 - 22.
The Associated Press contributed to this report.