Beginning with California and the North American West, his vision grew to include Mexico and Central America, through the Isthmus of Panama. Bancroft's writings and library covered Pre-Colombian indigenous populations to the modern societies of his times. The current thrust of collecting continues to build on those strengths with inclusion of new subjects and fields of scholarship that extend the broad, intellectual foundations of the original library. As a specialized area collection, the collection contains all forms of primary and secondary sources, including strong collections of bibliographical and reference sources, all forms of printed materials, and critical editions of major historical texts. The Bancroft Library collects widely on historical and contemporary Mesoamerican indigenous cultures.
Many works are in Indian languages.
Colonial Spanish America, 1492-1821, is the richest portion of the collection. Although focusing primarily on Mexico and Central America Bancroft holds a variety of sources on the Caribbean and South America. The large printed collection reflects the character of Spanish and colonial publishing of the time, in which religious and legal materials predominated over humanistic and scientific subjects. Contemporary insititutional research relies heavily on significant numbers of original manuscripts, supplemented by very large holdings of transcriptions, photostatic reproductions, and microfilm. Especially important are the microfilmed documents of the Spanish and Mexican archives, supplemented by microfilm of other European archives.