Polemonium eximium, or showy sky pilot, is endemic to California; in the wild, this species only occurs at high elevations in the Sierra Nevada.
Forty percent of California’s 5500 native plant species occur only in the state. Unsurprisingly, perhaps, California has the most native species of all US states (see: Why California harbors so many plant species). The question surrounding what factors determine such high biodiversity in specific areas of the Earth is a longstanding one. In the linked article, the research results suggest that California is an important refuge for species (i.e., it is not that new species are evolving there at rates faster than elsewhere, but rather that old lineages are better able to persist due to factors such as a mountainous topography).
Polemonium eximium is a caespitose herbaceous perennial that reaches 10 to 40cm (4 to 15 in.) in height. Its hairy flowering stems culminate in a blue or purple inflorescence. The plant pictured above had one remaining stem in flower late in the summer, but more examples can be seen on the CalFlora page: Polemonium eximium. Individual flowers are in full bloom for only a matter of days through the short-lived growing season. These attract pollinators with a pungent scent, apparently reminiscent of urine.
The name sky pilot likely comes from the association with high altitudes. For most people, embarking on a trek through the mountains is the only way to see sky pilot, unless one is (or knows) an expert alpine gardener. Like many high-altitude plants, they are tricky to grow and persist in cultivation! The species typically grows on talus or rocky outcrops at 3000 to 4200m (~10500 to 13100 ft.). According to Wikipedia, you are most likely to find it on Mt. Whitney, Mt. Langley, or on Mt. Dana of Yosemite National Park. However, an interactive sightings map on Jepson eFlora notes other locations where occurrences have been documented. This scarcity makes it one of the most rewarding wildflowers to find throughout the Sierra Nevada. On a webpage devoted to exploring Yosemite National Park, someone makes mention of a pleasant encounter with sky pilots on the summit ridge of Mount Lyell, where hordes of butterflies were busy pollinating them and concurrently getting eaten by birds. Further noted was how the birds then excreted what they ate to fertilize this group of sky pilots, offering a glimpse into the life cycles of organisms in the High Sierra (linked page also has photos–click on the Image Gallery tab).