Central and eastern Alaska, western and central Canada and western USA. Non-breeding south to south-western and south-central USA and western and central Mexico.
 
Population
Estimated population is 5,200,000 (2010).
Mountain Bluebird (Sialia currucoides) [XC205426]
by Richard E. Webster from Handy Drive, south of Carbondale, Pitkin County, Colorado, United States (song)
Mountain Bluebird (Sialia currucoides) [XC441350]
by Thomas Magarian from Opal City, Crooked River National Grasslands, Jefferson County, Oregon, United States (call)
Subspecies
No subspecies.
Has been suggested that specific name currucoides inapplicable, and that name arctica is required. Occasionally hybridizes with Eastern Bluebird (Sialia sialis).