Ethnohistory uses both historical and ethnographic data as its foundation. Its historical methods and materials go beyond the standard use of books and manuscripts. Practitioners recognize the utility of maps, music, paintings, photography, folklore, oral tradition, ecology, site exploration, archaeological materials, museum collections, enduring customs, language, and place names.
Ethnohistorians have learned to use their special knowledge of the groups they study, linguistic insights, and the understanding of cultural phenomena in ways that make for a more in-depth analysis than the average historian is capable of doing based solely on written documents produced by and for one group. They try to understand culture on its own terms and according to its own cultural code. Ethnohistory differs from other historically-related methodologies in that it embraces emic perspectives as tools of analysis. The field and its techniques are well suited for writing histories of Native American peoples because of its holistic and inclusive framework. It is especially important because of its ability to bridge differing frameworks and access a more informed context for interpretations of the past.
The definition of the field has become more refined over the years. Early on, ethnohistory differed from history proper in that it added a new dimension, specifically "the critical use of ethnological concepts and materials in the examination and use of historical source material," as described by William N. Fenton. Later, Axtell described ethnohistory as "the use of historical and ethnological methods to gain knowledge of the nature and causes of change in a culture defined by ethnological concepts and categories. Others have focused this basic concept on previously ignored historical actors. Schieffelin asserted, for example, that ethnohistory must fundamentally take into account the people's own sense of how events are constituted, and their ways of culturally constructing the past. Finally, Simmons formulated his understanding of ethnohistory as "a form of cultural biography that draws upon as many kinds of testimony as possible over as long a time period as the sources allow." He described ethnohistory as an endeavor based on a holistic, diachronic approach that is most rewarding when it can be "joined to the memories and voices of living people.