The National Park Service found the original deed from 1695 for the homestead in Virginia where George Washington was born and copies of John Peter Zenger’s New-York Weekly Journal from 1735 reporting on his landmark trial affirming freedom of the press. The Center for Jewish History discovered the 1944 document in which Raphael Lemkin coined the term genocide. The Morgan Library turned up a 1913 letter from the sister of Virginia Woolf saying that “Virginia was very much depressed yesterday” and attempted suicide — three decades before she would kill herself.

Those are among the nearly two dozen institutions that have received grants from the Leon Levy Foundation since 2007 to identify, preserve and digitize their archival collections and to make them available online to scholars and to the public.

The foundation’s archives and catalogs program has awarded more than $10.3 million, including two grants this week: $3.5 million to the Institute for Advanced Study in Princeton, N.J., to collect and conserve the papers of its present and former scholars, including George F. Kennan, J. Robert Oppenheimer and Albert Einstein; and $2.4 million to the New York Philharmonic, where archivists will digitize 1.3 million pages, including a 1909 Mahler score for his First Symphony originally marked up by the composer and further annotated 50 years later by Leonard Bernstein.

In some cases, institutions like the Roundabout Theater Company and Federal Hall in Lower Manhattan barely realized they held potentially valuable archives. In others, historic documents and artifacts were stored in vaguely labeled boxes but never cataloged. Still others, like the Philharmonic, lacked the resources to make their collections more widely available through digitization, which also preserves them by reducing handling...