According to a poll commissioned by 5280 magazine for its April 2012 issue, of 408 people in the Denver-Boulder-Colorado Springs "triangle" suggests that a huge proportion (compared to other historical surveys) are not Christian.
* 60% are Christian (excluding Mormon, Religious Science and Seventh Day Adventist)
* Less than 1% of Mormon
* Less than 1% of Muslim
* Less than 1% of Hindu
* 4% are Jewish
* 2% are Buddhist
* 13% are agnostic
* 7% are atheist
* 12% are "Other" (Tao'ism, Bahai, Living Light, Metaphysical, Shinto, Unitarian, Native American/earth religions, pagan, Religious Science, Scientology, Seventh-Day Adventist, Shamanism, Wiccan, yogic philosophy).
My basic reaction to this is "I wish." There is no way on this earth that 36%-40% of people in this region do not identify as Christian. Boulder, maybe, but not Boulder-Denver-Colorado Springs. I've seen half a dozen other sets of statistics on essentially the same issues and this is not their conclusion. The statistics might be a representative sample of 5280 readers, but not of adults in this region.
Also, self-described atheists and agnostics almost never make up that share of the the non-Christian population. In almost every other survey the largest category of non-Christians is "not religious" and does not attend church services but is "spiritual", often marginally theistic in a generalized way, and rarely self-identified as atheist or agnostic, some of which may be picked up in "other" but which is rarely as organized as the description of "other" implies.
Mormons (at least two denominations are active in Denver) and Seventh-Day Adventists (whose regional headquarters is in Denver across the street from the Adventist Hospital), both of whom absolutely self-identify as Christians, also probably don't like being treated separately from other Christians.
The 5280 story is an entertaining read with interesting insights, but it would be a mistake to afford much credibility at all to its statistics. The sample, however it was drawn, is clearly not randomly drawn or representative.