Lewis's woodpecker was described and illustrated in 1811 by the American ornithologist Alexander Wilson in his "American Ornithology; or, the Natural History of the Birds of the United States". Wilson based his description on some bird skins that had been collected on an expedition across the western portion of the United States led by Meriwether Lewis and William Clark in 1803–1806. Wilson coined the English name "Lewis's woodpecker" and the binomial name "Picus torquatus". Unfortunately, the specific epithet was preoccupied by the ringed woodpecker, "Celeus torquatus" (Boddaert, 1783) and so in 1849 the English zoologist George Robert Gray coined a new name "Picus lewis". The type locality is Montana. Lewis's woodpecker is now placed in the genus "Melanerpes" that was erected by the English ornithologist William John Swainson in 1832. The species is monotypic: no subspecies are recognised.