The oldest nut in the basket is the walnut, a family of over 15 nut trees native to Asia, Europe and the Americas. One of these, known popularly as either the Persian or the English walnut, is the most important worldwide. The walnut tree probably sprang up somewhere in a large area stretching from the south eastern portion of Europe through the Middle East and all the way north into the mountains of India. The wild tree's fruit was collected seasonally for thousands of years. Carried by people, dispersed by birds, too, the walnut traveled far and wide. The oldest walnut remains have turned up in the Shanidar Caves of Iraq, home to people living about 50,000 BC.

The domestication of the walnut probably began about 12,000 years ago. Stone Age tribes of 7000 BC who lived at the edge of Swiss lakes had these domesticated nuts by 7000 BC. The Greeks and the Romans were fond of walnuts, finding them far superior to the everyday acorns, chestnuts and beechnuts most people ate. In the Middle Ages walnuts were pressed for oil. Poorer people ate wild walnuts, and in desperate times, actually ground up walnut shells and mixed them with liquid to make a kind of bread.

Spanish padres brought walnuts for planting to the California coastal missions in the 18th century.

Walnuts are rich in omega3 fatty acids, benevolent fats that combat heart disease. They are one of the few plants in which these fats occur.