Though privately owned and operated, the library continues to provide free access to the public for the purpose of conducting research in science, medicine and technology.

His will donated approximately $2.6 million of his estate to Chicago as an endowment for a free public library, selected "to create and sustain a healthy moral and Christian sentiment, and that all nastiness and immorality be excluded."

The Board of Directors of the library established a building fund with the 1889 endowment and set out to gain approval for a Grant Park location.

In 1902, the Chicago City Council approved the plan, but public criticism forced the design to be built on the Northwest corner of Michigan Avenue.

[4] Following World War II, the John Crerar Library became one of the first to offer a fee-based research service which was targeted to industry and government users.

[10] The library now offers computer-based searches of a wide variety of scientific and medical data bases.

[13] The official motto of the John Crerar Library is engraved on its current building: Non est mortuus qui scientiam vivificavit (translation: "He has not died who has given life to knowledge")[11] The Crerar collection includes 27,000 rare books including works by Copernicus, Leonardo da Vinci, Descartes, Franklin, and Newton.