The U.S. is surely and steadily becoming a less religious place. USA Today has a groovy interactive graph illustrating the following:
The 2008 results [of the American Religious Identification Survey], to be released today, are based on 54,000 interviews with a margin of error of plus or minus 0.5%. It finds that, despite population growth and immigration adding nearly 50 million more adults, almost all denominations have lost ground since the first ARIS data was released in 1990.
Here's the picture of state-by-state growth in the number of people identifying as atheists, agnostics, or without a religion:
But go to the real graph for the groovy interactivity.
Secularization is part of a long trend toward moral liberalization. That the Iowa Supreme Court would unanimously rule prohibition of gay marriage illegal when a decade ago this would have seemed impossible is just one example of this very welcome trend.