The article advances the thesis that population growth in the United States reduced the privacy that Americans value and thereby became the common antecedent for two seemingly unrelated phenomena in the third quarter of the twentieth century — the emergence of two organizations concerned with domestic population growth, and a narrow judicial interpretation of law relevant to privacy. The thesis is supported by (1) data obtained in sample surveys I conducted of the members of Zero Population Growth and the members of the National Organization for Non-Parents, and (2) court opinions pertinent to the right of privacy.