A plan drawn in 1919 by university professor James M. White imagined a new southern quad anchored by a new library on its western edge.

During the economic prosperity that Illinois experienced in the Roaring Twenties, the state legislature committed to funding a major building campaign at the university.

In 1923, the University of Illinois hired landscape architect Charles A. Platt to revise the master plan and design new construction.

[4] To help accommodate an influx in enrollment following World War II, the University of Illinois opened a satellite campus in Galesburg.

[8] In 2019, the university announced plans to modify the Main Library by demolishing five of the six bookstack additions on the west side of the building, which will be rebuilt with five stories.

The new addition will accommodate interdisciplinary learning spaces, and compact shelving in the new basement will help compensate for the book storage lost by demolishing the stacks.

[10] The Main Library is one of the eleven red brick Georgian Revival buildings designed by Platt as part of his campus master plan.

The Main Library's lobbies, circulation spaces, and second-floor reading room retain their elaborately-detailed historic features.

The reading room has 27 stained glass windows showing Renaissance printer's marks, and four Barry Faulkner murals decorate the walls of the central stairwell.

Its counterpart in the north lobby is the plaster model of Thomas Hopkins Gallaudet and Alice Cogswell by David Chester French.

[15][16] Its collections, consisting of over half a million volumes and three kilometers of manuscript material, encompass the broad areas of literature, history, art, theology, philosophy, technology and the natural sciences, and include large collections of emblem books, writings of and works about John Milton, and authors' personal papers.