This article was originally published in the August 1976 National Geographic.
I gazed in amazement at the sight. Butterflies—millions upon millions of monarch butterflies! They clung in tighty packed masses to every branch and trunk of the tall, gray-green oyamel trees. They swirled through the air like autumn leaves and carpeted the ground in their flaming myriads on this Mexican mountainside.
Breathless from the altitude, my legs trembling from the climb, I muttered aloud, “Unbelievable! What a glorious, incredible sight!”
I had waited decades for this moment. We had come at last to the long-sought overwintering place of the eastern population of the monarch butterfly.
Every wide-eyed child and meadow walker in the eastern United States and nearby Canada knows this colorful butterfly, by sight if not by name. It skims and dips in summer over fields and gardens from Texas to England, from Florida to Minnesota. But in winter the monarch vanishes from the regions. Where does it go?