Two Monarch Butterfly Populations
in North America

Click map to enlarge
There are two migratory populations of monarchs in North America.

There is much uncertainty about the exact distribution of these populations!

What follows is a generalized summary.

Eastern Monarchs (in red on map):
The bigger monarch population breeds east of the Rocky Mountains throughout much of the central and eastern U.S. and Canada
. They overwinter on 12 mountaintops Mexico. Most Journey North migration reports highlight sightings of these eastern monarchs.

Western Monarchs
(in yellow on map):
There are 200 to 300 small monarch colonies that winter within 5 miles of the Pacific Coast from Ensenada, Baja California (31.5 N latitude) to Marin County, California (38.1 N latitude). The breeding ground resources are not known, but are assumed to run from California north to Washington and across the Sierra Nevada to Nevada and other western states.

More About Western Monarchs