The three largest mass mobilizations ever witnessed in this country occurred in 2006 on March 25th, April 10th, and May 1st, when undocumented immigrants and supporters marched against repressive enforcement-only antiimmigrant legislation and then for immigration reform. Academics have since scrambled to understand these mobilizations. Some misguidedly labeled the Latino community as a "Sleeping Giant." Contrarily, interviewed in this research were dozens of veteran Immigrant Rights Movement (IRM) activists who illustrated that there is a longstanding immigrant rights struggle in the cradle of the IRM, Los Ángeles, the majority of which have been mobilizing against repressive antiimmigrant legislation as far back as the 1960's. Drawing from the social movement literature, this dissertation utilizes two dominant concepts to examine the IRM - the political opportunities and resource mobilizations models. From the dual perspective of a participant and researcher, the present researcher examines the IRM's organizational history in order to understand the decision-makers, while paying closer attention to the efforts leading up to and during the spring 2006 mobilizations, thus providing a unique contribution to this literature based on an insider perspective of the Movimiento. In this analysis, two factions in the IRM emerge, the leftist faction that includes both the radical and traditional factions of the Movement, and the moderate faction that represents the elite level of the IRM. The traditional faction by itself has gained much respect amongst the immigrant rights community in LA and has a history of working with either the radical or moderate factions. This research found the necessity for a future examination of the immigrant community's response to join in the IRM's mobilizations to investigate more systematically the effectiveness of leaders and organizations in their mobilizing efforts by which to guide the immigrant rights community's future endeavors. It also challenges other students of social movements and Latino Studies to involve themselves in the Movimiento to garner first an insider perspective that would draw a more in-depth look into the inner-workings of the IRM, thus reliably adding to the extant social movement literature, the burgeoning literature on the IRM, and Latino Studies.