And the Winner is.... Pete Stark, representing the East Bay

As aaronjv already announced, the nontheistic Congresscritter is Pete Stark of California. Nixon was still president when Stark was first elected to the House, which makes him a fossil with a great deal of seniority. He's chairman of the Subcommittee on Health of the House Committee on Ways and ... oh heck, if you're interested, just read Wikipedia's entry on him.