The transnational turn has both expanded and reshaped US-Mexico borderlands history, prying the field from regional matrices and binational binaries. Frontiers in the Gilded Age jumps into this fray as a “transnational frontier history” that entangles US West, Mexican, and African stories, with a primary focus on white male adventurers and their families (p. 3).Andrew Offenburger first discusses what he calls the “western turn South,” as adventurers on earlier US frontiers crossed into Mexico, motivated also by romances of empire in Africa (such as H. Rider Haggard's King Solomon's Mines) (p. 30). They saw Mexico as a new Africa: a treasure house of lost riches, a land ripe for penetration. With parallel mining booms, the United States, Africa, and Mexico were also linked in fact by a “network of adventurers, settlers, miners, and families” (p. 53).Frontiers in the Gilded Age approaches these entanglements through border-crossing stories, linked in idiosyncratic ways. We start with Frederick Russell Burnham—a Minnesotan raised on Victorian adventure tales, who fought Ndebele warriors under Cecil Rhodes in Africa before moving to Mexico to defend US corporate interests against Yaquis. Burnham traveled with his family on a global circuit leading across the US West, southern Africa, Yukon, and West Africa to the Río Yaqui. We leap next over the Sierra Madre to meet James and Gertrude Eaton, who crossed south from the United States to Chihuahua in 1882 as part of a larger, global community of Protestant missionaries. Offenburger asks how family and gender structured mobility across borders while also entangling the Eatons with fellow border crossers in Chihuahua—exiles from the former Boer Republics of Africa.The Boer story takes us back to Africa, to battles against the British empire, where we follow rebels Willem Snyman and Benjamin Viljoen into exile. We follow them first into the United States (where they seek support for their diasporic community by reenacting their role as white African rebels in Wild West shows) and then to Chihuahua, first as colonists under Porfirio Díaz and then as soldiers of fortune after 1910. Benjamin Viljoen is the most developed of Offenburger's characters, a white anti-imperial warrior later steeped, in Wild West shows and as author of his own romanticized tale, in the rhetoric of empire. In the final chapter, we follow him to Sonora as an agent appointed by Francisco Madero to the Río Yaqui (where by this time the likes of Burnham and Haggard have traded their African adventures for new Mexican ventures). As the former freedom fighter begins negotiating with Yaquis on behalf of empire, Offenburger flips the lens one last time—drawing on oral histories of the Yaquis (as migrants and exiles in their own right) to offer a different view of this frontier. Adventurers will come and go as the Yaquis—“persistent, stalwart, resolute”—have the final word (p. 196).This is an engaging, humanized book. Offenburger calls it a frontier history, but the frontier is most visible and convincing as a literary realm that adventurers pilfer in acts of self-fashioning. Frontiers in the Gilded Age is more an entangled history—an idiosyncratic, open-ended view of nineteenth-century crossings and convergences. Offenburger's analysis of frontier rhetoric and self-fashioning is sound, and his parsing of British and US literary strands compelling. What is missing is a rigorous analysis of the central notion of adventure, at a time when it meant different things in romantic tales and actual risky ventures. While some rejected Burnham's tales of adventure as “campfire stories,” Offenburger notes, “there is no question he led a life of adventure” (p. 63). This may be, but without knowing what adventure meant on the ground (as a constellation of high-risk practices at the edges of markets and states), readers may find it hard to fully comprehend the grounded dynamics behind these border-crossing gambles.Offenburger is, in fact, ambivalent about focusing too hard on these white men. Because they “were prone to embodying a hypermasculinity, to denigrating indigenous peoples, and to romanticizing the American frontier,” he strives to “offset their bias” by focusing when possible on women, families, and Indigenous perspectives (p. 9). Especially with the Eatons, he demonstrates why we cannot understand border-crossing networks without attention to women and family. His use of Yaqui oral histories is also effective, so much so that it destabilizes his larger frame. If Indigenous peoples and not adventurous newcomers are to have the final word—that is, if we seek a transnational history beyond empire—then the next step might be to approach the histories of the United States, Mexico, and Africa from multiple Indigenous perspectives. In questioning characters and frames, Frontiers in the Gilded Age may do its most provocative work by suggesting an alternative path forward.