The Adler Planetarium's History of Astronomy Collection contains almost 2,000 historic instruments. This makes it the largest collection of such material in the Western Hemisphere and one of the largest and most important in the world.

The Adler's Rare Book Collection contains over 2,000 volumes, including over a dozen incunabula, books printed before 1500. The rare books cover a wide range of topics about the history of astronomy and scientific instruments. Related to the Rare Book Collection is the Adler's Works on Paper Collection. It contains about 550 individual maps, prints, and book plates featuring astronomical illustrations. Strengths of this collection include comet and eclipse broadsides, portrait prints, and celestial charts.