Recent discussions of Margaret Fuller and her accomplishments concentrate on her gradual transition from Transcendental idealism to social activism. David M. Robinson calls Fuller's Woman in the Nineteenth Century the "bridge" between these two ideologies, yet other scholars have cited Fuller's journey to the Great Lakes region and Summer on the Lakes, in 1843, the book that resulted, as the first stage of her "centrifugal career" (Chevigny). I believe an examination of Summer on the Lakes will demonstrate that the latter is a more accurate description of Fuller's evolution. Because Summer has not been more than cursorily examined in this light, this paper's purpose is to analyze Summer on the Lakes as a component of Fuller's waning interests in Transcendentalism as theory and an indication of an increasing commitment to social activism. This paper will also examine Summer on the Lakes as exceptionally valuable evidence of Fuller's skill as a writer.