The importance of the letter as a means for social, personal and intellectual expression for humanists has been highlighted in various studies. For those studies, its value resides in its effectiveness in responding more directly to the presence of a new pool of readers giving rise to a new cultural type, transforming it into the emblematic genre of the humanists. I am interested in considering the influence of epistolary models in the New World, because, as these models were transferred to a new context, they acquired new forms that responded to the needs of communication, representation, symbolization and, finally, a new rhetoric. For the purposes of this dissertation, I will depart from the conception of the letter in the New World as a “polysynthetic” genre; that is to say, inasmuch as I wish to respond to the plurality of communicative needs that arose from the new contexts that were unforeseen by the humanist rhetoric, I will consider the letters from the New World as emerging from and forming part of other genres: accounts, petitions, diaries, among others. The starting point for this dissertation is the thorough reading and analysis of eleven unpublished letters, all written by women, currently located at the Archivo General de Indias in Seville and sent from the Rio de la Plata during the XVI and XVII centuries. In my investigation, I intend to demonstrate how the authors used the writing of such documents as an empowering practice. Secondly, I will prove that these first epistles, written from America, do not necessarily belong to the ars epistolandi, but to the ars dictaminis. Furthermore, this change in disctinction requires a critical review of the current state of classical letters. Finally, I maintain that these letters provide a space for the emergence of the authors‟ identity. In other words, I understand and ground the conclusions of this work on the fact that space culturally shapes gender, but that gender acts in the production of such spaces as well. The participation of female authors by means of these letters merges them with that spatiality in a process both of production and reproduction, since, as a conscience building act, the “I” is turned into text in order to discuss on/about the space.