The hazelnut (Corylus avellana) was designated the official state nut of Oregon in 1989. Oregon grows 99 percent of the entire U.S. commercial crop of hazelnuts. The unique texture and marvelous flavor of hazelnuts make them a favorite of chefs, bakers, food manufacturers, and cooks around the globe. Hazelnuts are rich in protein and unsaturated fat.

Hazelnut is popular as a coffee flavoring, is used to make praline for confections, is ground as a popular nut butter spread (more nutritious than peanut butter), used in many delicious chocolate combinations, and is also used to make vodka-based hazelnut liqueurs.

Pecans, black walnuts, and peanuts are also official state symbols (see list of state food symbols).

Source:

State Symbols: Oregon Blue Book
Hazelnut: Wikipedia.org

Links:

American Food and Agricultural Symbols
American Food Holidays