During the Argentine (1976-1983), Chilean (1973-1990), and Uruguayan (1974-1980) dictatorships, systematic state repression violently restricted possibilities for communal exchange, access to public space, and collective dissent. The human rights abuses waged by the regimes included the kidnapping, torture, and execution of presumed "subversives" without a trial. After the transition to democracy in these countries, citizens agitated against amnesty laws that protected military officials and prevented families from obtaining information regarding the whereabouts of their disappeared (kidnapped and executed) relatives. This thesis explores how resistance to these regimes and the memory politics forged in their wake hinge on simultaneously creative and political acts of assembling. The focus is on artistic projects that facilitated identification, dissent, exchange, and debate during these contexts of political repression, and those that have responded to the political demands of collective and generational memory in their wake. The projects comprising my corpus all experiment with various practices of assembling, defined as a simultaneously aesthetic and political practice, to foster moments of exchange, contact, and contingency. My analyses develop at the nexus of political assembly (Butler) and assemblage philosophy (Deleuze and Guattari). From these philosophical coordinates, I think through ten projects that engage with material and social precariousness, historical memory and elemental shame, a political consciousness that extends beyond the human, reciprocal exchange, and networked forms of witnessing. In the first chapter, I bring together two works in which portraits of the disappeared were introduced into the city centers of Buenos Aires and Montevideo: the afiches participativos by C.A.Pa.Ta.Co. (1984) and Juan Ángel Urruzola's Miradas ausentes (en la calle) (2008). The second chapter explores how a politics of recognition informs the passage of trauma within and between generations, considering the role of "elemental shame" (Arendt), or shame as a mode of seeing, in León Ferrari's Nunca más collages (1995) and Lucila Quieto's configurations of the "familial gaze" (Hirsch) in the collaged family photo album in Filiación (2013). The third chapter develops a theory of recognition that extends to include the non-human through a comparison of Cecilia Vicuña's Saborami (1973) and Graciela Gutiérrez Marx's ediciones de con-fusión (1980-1983). In chapter four, I compare Marcelo Brodsky's collaborative project Visual Correspondences (2008) with the reciprocity described and attempted by a 1986 piece of correspondence by mail artist Edgardo Antonio Vigo. The fifth and final chapter proposes a notion of "networked witnessing," a form of collective witnessing defined by digital and analog social networks, in relation to a 1977 mail art initiative to free two Uruguayan artists from prison and an Instagram page of analog collage documenting the 2019 protest movement in Chile. Illustrating the links between art, activism, historical memory, and human rights in the Southern Cone, my thesis proposes specific historical and theoretical anchors for interpreting the mutual endurance and entanglements of creative practice and political assembly.