I realized that I had photographs of most local species in the Ericaceae (or heath family), with the main exceptions being good images of Vaccinium spp. and Pyrola spp., so I am now in the process of developing a presentation on the family (and photographing for the gaps). On the strength of this plant walk description of the Olallie Meadows near Seattle, I decided to visit the area a couple weekends ago to photograph some blueberry species while in the area. I didn't see as many berries as I hoped; perhaps the area was already picked over. Certainly, the bears had visited from some evidence on the path. Still, I did see the three species highlighted in the write-up. Vaccinium ovalifolium was very common, and, as the author of the linked write-up noted, "well worth eating but not as tasty as the other two [Vaccinium membranaceum and Vaccinium deliciosum]".
Oval-leaf blueberry or early blueberry has a mildly curious distribution. The species can be found in east Asia (Japan and far east Russia), northwestern states and provinces in North America, South Dakota, Michigan and eastern provinces of Canada. Its typical habitats as stated in Flora of North America are "Moist or mesic coniferous woods, transitional habitats adjacent to these coniferous stands, cut-over coniferous woods, verges of road cuts, margins of coniferous woods, peaty slopes". This maps well to the typical association of blueberries with slightly acidic soils.
Additional photographs (including photos giving a bit more perspective of the plant) of oval-leaf blueberry are available from the Burke Museum: Vaccinium ovalifolium.