It is endemic to the forests in the higher elevations of the Sierra de la Laguna mountain range of the southern Baja California peninsula in Baja California Sur, Mexico.

[4][5] The type specimens of Baird's junco were collected on February 2, 1883, by Lyman Belding at "Laguna, Lower California" [=Baja California], and it was named for Spencer Fullerton Baird, an American ornithologist and naturalist, by Robert Ridgway, the curator of birds at the United States National Museum at that time.

[8] Baird's juncos are sexually monomorphic, and adult Baird's juncos have gray heads with black lores, buffy brown backs, wings, and flanks, and paler gray or white throats blending into a pale whitish chest, belly, and vent.

Baird's junco is restricted to the higher elevations of the Sierra de la Laguna, Baja California Sur, Mexico, where it nests in pine-oak forests.

[6] This species is largely restricted to the higher elevations above 1,500 metres (4,900 ft) where appropriate habitat occurs, but non-breeding individuals do wander lower down, with previous sources considering the bird common above 3,000 feet (910 m) in elevation[10] and more contemporary sources noting records as low as 700 metres (2,300 ft) in elevation.