One of the characters that most helps in identifying a Douglas-fir is the set of long, three-pointed bracts on the cones. While the distinct flexing in the bracts could have been enough for me to identify this particularly as Rocky Mountain Douglas-fir, the fact that it was located at the foot of the Rocky Mountains served as my main clue.
Pseudotsuga menziesii var. glauca, or Rocky Mountain Douglas-fir is also commonly known as interior Douglas-fir (see a previous BPotD entry). This tree taxon can grow to 50m (164 ft.), somewhat shorter than its (west) coastal relative, Pseudotsuga menziesii var. menziesii. Its distribution in continental North America ranges from Alberta to southern Mexico. E-Flora BC details some of the other differences between the two varieties, stating that Pseudotsuga menziesii var. glauca has both shorter cones with a greater degree of bract-flexing and foliage that is often more bluish-green (the epithet for this variety, glauca, means blue-green in Latin). In both varieties, the bracts on the female cones extend past the cone scales, but are typically straight in the coastal variety. Similar to the coastal variety, Rocky Mountain Douglas-fir is highly valued for its strong timber.
Nomenclatural history of Douglas-fir seemed like quite the nightmare in the 19th and 20th centuries. Many names were applied and rejected, leading to prolonged discussions on the topic. During much of this time, Pseudotsuga menziesii var. glauca was given a sequence of varietal names as it became distinctly recognized from the coastal variety. Around 1950, the scientific names we use today were established. A third variety, var. caesia, was described around the turn of the 19th century as an intermediate form of the two currently-recognized varieties, but was discredited after roughly 50 years. More information can be found in this history of the genus Pseudotsuga (PDF).