Welfare aid in the USA groups close to means-teste programs and all targeted on categories of people, and mainly on households with children. The majority of these benefits which make up “Welfare” were subject during the 1990’s to various reforms which, by reinforcing the principle of counterpart and by favouring a return to employment, also modified the functions of welfare aid. In addition, the main reform of welfare aid which occurred in 1996, setting up a system of “Workfare” at the federal level, accentuated the autonomy of the States in managing and defining such programmes. Any analysis of this reform and its applications is generally made at the national level, but important differences appear when one targets study onto the welfare aid policies followed by the federal States. This is the viewpoint taken by this article which above all seeks to describe the disparities in the institutional devices set up by the federal States, their different strategies regarding welfare policy, and their impact on poverty levels. The analysis by case types allows one to illustrate the variations observed between States in more concrete terms.