This paper examines how the definition of family, within Federal public housing and welfare policy, corresponds with changes in family patterns in America from 1950 to 2000. The definition of family as used to determine welfare eligibility is extremely important not only for how it defines recipients of cash aid but also because of how it affects public housing clients. In the name of economic vitality, needy individuals might choose to define their family according to the lowest common denominator to gain access to both welfare and public housing, thus negating diverse forms of family. Since family definition serves as an important gate-keeping device for program benefits to otherwise eligible families, it is important to establish if policy definitions of family reflect changing patterns of need or perceived normative definitions of "proper" family form. While public housing policy is the focal point of this research, it is necessary to review both housing and welfare policy to ascertain the impact of welfare policy's definition on overlapping participants. The changes in policy definition will be juxtaposed with cultural and legal shifts in family form to explore the policy's interaction with larger social trends. Public housing and welfare policy beginning with their respective inaugural legislation, the Wagner-Steagall Housing Act of 1937 and the Social Security Act of 1934, and their subsequent revisions are examined to track modifications to family definition. U.S. Census Bureau Current Population Reports, Series P20-537, "America's Families and Living Arrangements" data from 1950-2000 and Persons of Opposite Sex Sharing Living Quarters (POSSLQ) forecasting have been used to track social trends related to family composition patterns. Additionally, Federal and State Supreme Court rulings related to family formation and Domestic Partner legislation in California and Vermont have been used to gauge the legal legitimacy of varying family forms. Among the study's findings is public housing legislation's ongoing broad definition of family, the degree of influence welfare policy has historically had on the family form of public housing residents, and public housing's new "mixed family". Recommendations for future research include an examination of public housing's new "mixed family" issue and an examination of the impact on family form of the current public housing and welfare legislation: Quality Housing and Work Responsibility Act (QHWRA) and Temporary Assistance for Needy Families (TANF).