Webster's Revised Unabridged Dictionary · 1913

Dalles

Dalles (dalz) , noun, plural

[French dalle a tube, gutter, trough.]

A rapid, esp. one where the channel is narrowed between rock walls. [Northwestern United States & Canada]
The place below, where the compressed river wound like a silver thread among the flat black rocks, was the far-famed Dalles of the Columbia. — F. H. Balch