The Secular Coalition for America has done some investigating and come up with this:
There is only one member of Congress who is on record as not holding a god-belief.
Rep. Pete Stark (D-Calif.), a member of Congress since 1973, acknowledged his nontheism in response to an inquiry by the Secular Coalition for America. Rep. Stark is a senior member of the powerful House Ways and Means Committee and is Chair of the Health Subcommittee.
Although the Constitution prohibits religious tests for public office, the Coalition's research reveals that Rep. Stark is the first open nontheist in the history of the Congress.
Surveys vary in the percentage of atheists, humanists, freethinkers and other nontheists in the U.S, with about 10% (30 million people) a fair middle point. "If the number of nontheists in Congress reflected the percentage of nontheists in the population," Lori Lipman Brown, director of the Secular Coalition, observes, "there would be 53-54 nontheistic Congress members instead of one."
Given the number of congresspersons who seem to be completely bereft of any sense of ethical obligation or conscience I suspect that Ms Brown's estimate is a little low.
RLC