This compact volume is an indispensable study of state imaginaries and the political economy of development in Colombia's contemporary internal conflict. In contributing to a growing literature that contests metanarratives of the Colombian state's absence or failure, Teo Ballvé also accounts for the power and persistence of right-wing paramilitarism. Ballvé convincingly argues that the supposed absence of the state in northwestern Colombia's banana-growing frontier region of Urabá does not explain the violence that gripped the region for decades. Instead, those “clashes between insurgency and counterinsurgency . . . were conflicts over the form and content of statehood itself” (p. 35).Ballvé’s key conceptual intervention is “the frontier effect,” which he defines as the process by which “claims of statelessness . . . shape the imaginaries, practices, institutions, and relationships of political life” (p. 5). The book follows the frontier effect's enactment from roughly the 1960s until the late 2010s, through an accumulating series of political and development projects launched by state, nonstate, and international actors. Chapter 1 narrates the place of Urabá in the twentieth-century imaginary of Antioquia's regional capitalist elites and explores “the paradoxical quality of frontiers as spaces produced by both the power and the limits of reigning regimes of accumulation and rule” (p. 18; emphasis in original). The establishment of United Fruit Company operations in the 1960s was soon followed by the arrival of insurgent groups, discussed in chapter 2. The Fuerzas Armadas Revolucionarias de Colombia (FARC) in particular took advantage of Urabá’s nascent institutional matrix to build “territorial hegemony” through banana workers' unions, state-sponsored community action councils, campesino cooperatives, and elections (p. 39). Echoing other regional studies of the FARC, Ballvé demonstrates that “guerrilla-controlled territories were not antistate or states in waiting” but rather “were intricately intertwined with well-established, formal governmental practices and institutional formations” (p. 43). The production of space is a central concern here, as Ballvé makes critical use of Henri Lefebvre to illustrate how the frontier (and by extension the state) was “at once conceived, perceived, and directly lived” (quoted in p. 33).Gramscian notions of hegemony provide the theoretical underpinnings of the book's next two chapters, where Ballvé introduces the notion of “paramilitary populism.” In contrast to “accounts of Colombia's armed conflict [that] position paramilitaries as all-powerful victimizers,” Ballvé compellingly posits that the paramilitaries built some degree of popular consent in Urabá by “position[ing] themselves as state makers” (pp. 148, 60). Drawing directly on insurgent practices and personnel, paramilitaries in the 1990s and early 2000s thickened Urabá’s local institutional matrix, as Ballvé discusses in chapter 3. Chapter 4 explores paramilitary efforts at the regional and national levels, as paramilitaries “turned statelessness into an affirmative political project of regional affirmation and state formation that tried to reconcile their narrow self-interests with practices of grassroots political participation” (p. 84). Murder, displacement, and dispossession would never be supplanted in the paramilitary repertoire, but neither were they its entirety.Ballvé’s argument about Urabá’s “sedimented histories” becomes more explicit in the book's final three chapters (p. 151). Where paramilitary statecraft repurposed insurgent practices, paramilitary-created local institutions survived beyond the group's formal demobilization, in part because those institutions mobilized the language and forms of grassroots development to acquire financial support from state and international agencies. Ballvé explains in fascinating detail in chapter 5 how these tactics simultaneously strengthened the paramilitaries' popular legitimacy and formalized lands they had illegally acquired by force. Even when the state asserted its presence to an unprecedented degree in the 2010s, land restitution programs often worked through the channels of influence retained by Los Urabeños, the Urabá-born paramilitary successor group that remains Colombia's most important, as Ballvé highlights in chapter 6. Chapter 7 returns to the theme of capitalist imaginaries, examining neoliberal proposals for Urabá’s future that had their origins in the paramilitary projects of the preceding decades.Although Ballvé’s analysis extends across chronological and spatial scales, he is less successful at placing his case study in a national setting. For example, how typical or unique was Urabá compared to other Colombian frontiers? One could reasonably assume that the level and kinds of influence projected by its regional metropole set Antioquia apart; that is, neither Cúcuta nor Villavicencio is Medellín. To help extend his analysis, Ballvé could have looked to other recent English-language studies of Urabá, including Abbey Steele's Democracy and Displacement in Colombia's Civil War (2017) and Leah Anne Carroll's Violent Democratization: Social Movements, Elites, and Politics in Colombia's Rural War Zones, 1984–2008 (2011).Ballvé has nevertheless delivered us an impressive and timely book whose conclusions carry substantial explanatory weight beyond the confines of Urabá. Ballvé’s previous experience as a journalist—which included interviews with imprisoned paramilitary and FARC commanders—enhances the extensive ethnographic work that undergirds this eminently readable study. By highlighting the imbrication of violence, institutional rule, and development, The Frontier Effect will remain a vital guide to Colombia's ongoing yet fragile transition away from internal conflict, as well as to the nature of informal and formal politics in the contemporary world.