This paper studies the impact of the Great Mississippi Flood of 1927 on religious participation. We find a sharp increase in church membership in flooded areas that persists into modern times. This increase is more pronounced in conservative churches that provided more social insurance to members and had larger social costs to join. Access to alternative forms of insurance reduced the flood‘s impact on the uptake of church membership, consistent with religious organizations acting as social insurance providers. The flood did not affect families‘ likelihood of choosing religious names for their children: a more costly measure of religious belief