The Nontheist in Congress has been revealed. From Secular.org:
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 (www.secular.org ). Rep. Stark is a senior member of the powerful House Ways and Means Committee and is Chair of the Health Subcommittee.
The Secular Coalition is encouraging people to write Representative Stark for taking this step. An example letter can be found here.