Brittle Sandwort-Minuartia nuttallii ssp. fragilis

This pretty alpine plant growing over 10,000 feet is Brittle sandwort (Minuartia nuttallii ssp. fragilis). Another common name is Nuttall's sandwort. It's part of the Pink Family (Caryophyllaceae), and found only in Washington, Oregon, California, and Nevada.

The flower often grows in large mats of plants, but is less than half-inch across, so you have to be looking for it.
For more information about brittle sandwort, click here.