The South American wars of independence were rich in social contradictions, politicization of the masses and new players emerging during the Spanish Empire's crisis on the continent. By adopting a regional perspective that decentralizes and democratizes knowledge relative to state-centered nationalistic historiography, researchers can analyze episodes and discover historical players previously absent from state-of-the-art research. This paper traces a specific case related to the right to profits from Tarapaca guano during the 1815 patriot invasion of the district of Tarapaca and the River Plate offensive in neighboring Upper Peru. Based on unpublished primary sources and pertinent bibliographic discussion, the authors argue that socio-ethnic factors, interests and new conceptions about the use of regional resources drove a sector of South American society to support the Patriot cause temporarily. Thus, the political, economic and social conflict surrounding guano constitutes new background for the transformation of South American colonial society at the dawn of the 19th century and the imminent emergence of the republican order in southern Peru.