The purpose of this study was to find out under what philosophical influences public libraries in America developed in the middle of the 19th century. The study focused on individualism and pragmatism, and analysed the process of the development of public libraries under such philosophies. Individualism is the notions of the ultimate moral principles of the supreme and intrinsic value of the individual human being, the notion of individual self-development, the notion of self-direction or autonomy, the notion of privacy.  Pragmatism is a way of realistic, practical thinking that came from the frontier spirit and the influences of empiricism, the theory of the survival of the fittest and modern science. These changed people's mind in politics, society, education etc. Such changes promoted the development of the public library.