The Mission Blue butterfly ranges from the southern part of Marin County down the San Mateo Peninsula to whereabouts of Crystal Springs Reservoir. It has been observed at the Marin Headlands, Oakwood Valley, Twin Peaks, San Bruno Mountain, Sign Hill, Milagra and Sweeney Ridges. It inhabits small specks of grassland and rocky outcrops along these coastal hills and ridges.

Starting at the north and going south: