Fresno, the Spanish word for ash tree on maps of Upper California (Alta California)

Fresno is the Spanish word for ash tree. This word is found in geographical names identifying locations in Upper California (Alta California): Fresno River, Fresno County and the city of Fresno.

The Fresno River, whose water originates in the Sierra Nevada Range, is a major tributary to the San Joaquin River of the southern part of California's Central Valley. Fresno is the largest city of the San Joaquin Valley and currently the fifth largest city of California. Fresno is the seat of Fresno County. The county is said to be named after Fresno Creek, found in Spanish-language-annotated maps from the days when Upper California was “explored” by Spanish-speaking missionaries from Mexico.

Fresno is typically associated with the ash tree species Fraxinus velutina, which occurs in the southwest region of the United States and northern Mexico. Its common name is Velvet Ash, but the terms Modesto Ash, Arizona Ash or Desert Ash are also used. The range of the velvet ash overlaps with that of the Berlandier Ash (Fraxinus berlandierana), also called Mexican ash. The range of the Oregon ash (Fraxinus latifolia) also includes parts of California, but, as the name indicates, this species is more common in moist habitats along the coast of Oregon and Washington.

Ashes are of genus Fraxinus belonging to the olive family (Oleaceae). Ash species grow in various countries of the Americas and on other continents, where they also play a role in composing geographical names. In Germany, for example, the town names Eschenbach, Eschwege, and Eschweiler hint to the presence of ash trees (Eschen or Eschenbäume in German) during the making and naming of these German fresno settlements.

References
[1] The Smithsonian Guide to Historic America • The Pacific States. Stewart, Tabori & Chang, New York, 1989; pp. 162-163.
[2] Fresno County History at http://freepages.history.rootsweb.ancestry.com/~hummingbird/Fresno-County/fresnohistory.html.
[3] D. A. Sibley: The Sibley Guide To Trees. Alfred A. Knopf, New York, 2009; pp. 375-388 (Olive Family).