As many as 20,000 people are preparing to converge on the National Mall this weekend, united by their lack of belief in the kind of higher power promoted by most religions.
It's billed as the Reason Rally and some participants are calling it Woodstock for Atheists.
Some say it will be the largest gathering of its kind ever.
Head of the Beltway Atheists, Rick Wingrove will be one of thousands expected to attend, sending a message of separation of church and state to elected leaders.
"We would like to have a say when a bunch of angry white Christians are deciding our fate," says Wingrove.
A Pew Forum finds 16 percent of Americans are atheist or agnostic. And the numbers are growing.
This will be the second time such a rally has been held. The first was in 2002.