In the United States, today, immigration news unfolds like rapid fire. Since the late 1990s there has been no significant immigration legislation. As migratory patterns shift, like the uptick in Central Americans fleeing violence over the past few years, and immigration policy stagnates, regulation mechanisms cannot keep up. Tensions over national identity – as well as who ‘deserves’ to emigrate – resurface: in debates over the proposed border wall, in media coverage of the migrant caravans, and in public outrage over the detention of parents and their separation from their children at the border.

In Porous Borders, Julian Lim takes us into the myopic of unfolding relations in the San Antonio border region to argue for a bilateral understanding of immigration control of the US borderlands, one that is ‘a shared venture among states’ (p. 200). This observation, alone, makes the book highly instructive for our current moment. We clearly cannot understand current migration-related ‘crises’ as resulting from political shifts within the United States alone, but must recognise the interrelationships with socio-political realities within Mexico, Guatemala, Honduras, El Salvador and the region more broadly. And, we need to reflect on how the ‘border’ that we so contentiously debate today was constructed, by whom, and the specificities of its historical genesis, namely the period that Lim focuses on in this book: 1880 to 1930.

Lim's account includes details not widely incorporated into the US popular imagination due to a one-sided account of our nation-building processes. One of the book's first concrete examples to capture my imagination is that of slaves fleeing on an underground railroad south where sympathetic Mexicans left floating flatboats in the Rio Grande to aide those seeking refuge in northern Mexico (p. 57). I, like many children in the United States, grew up on legends of following the drinking gourd to the North Star to freedom, not this southern route. Similarly, Lim incorporates accounts of borderland indigenous groups – most extensively the Apaches and Yaquis. The ‘blueprint’ of immigration control, Lim argues, is the deterritorialisation of ‘autonomous indigenous groups who had exercised their sovereign authority by enforcing their own immigration policies over their lands’ (p. 25). The manner by which state actors in both the United States and Mexico interfaced with these groups helps explain their shifting experiences of inclusion and exclusion, particularly during the upheaval of the Mexican Revolution. Although we generally think of Mexico's national discourse post-revolution as embracing indigeneity, and the United States as negating this history, indigenous groups on both sides of the border moved between spaces of visibility and invisibility during this period.

Lim's bilateral perspective also sheds light on the regulation of Chinese individuals in the two countries. US federal immigration policy restricted Chinese immigration starting in 1882; this led to the expansion of Chinese settlements into northern Mexico and, later, with a deportation campaign targeting Chinese residents in Mexico, most pointedly in the state of Sonora. For Chinese individuals, daily life on the borderlands was a story of navigating exclusionary policies that, over time, began to coalesce and work in tandem with each other. In one remarkable example, Lim writes of Mexican officials depositing Chinese residents with US officials at the border to be deported to China at the expense of the US government. Vivid details like these illustrate how immigration control evolved into a shared project of two nations by the first quarter of the twentieth century.

Through this prism of multilateral perspectives, Porous Borders gives voice to often-ignored actors in history making. The book draws on an impressive array of primary data sources in both Spanish and English – from letters, newspaper accounts and photographs to historical accounts and reflections of seminal writers like Langston Hughes and W. E. B. Du Bois. Lim thereby reveals multiple actors, many of whom have been erased in modern renderings of US and Mexican history. My favourite insight of the book is the following: ‘Borders remain porous even as they thicken, and marginalized subjects persistently find ways to renegotiate the boundaries of racial and national identity envisioned by those in more formal positions of power’ (p. 199). Lim's creative use of uniquely personal accounts shows how the borderlands were not, in actuality, built by state actors, but rather arose out of a dynamic relationship between mobile individuals caught up in these state systems and emerging nation-states’ reactions to their mobility.

Chapter 2, ‘A Promiscuous Crowd’, best illustrates this insight. Here Lim tackles an important, often overlooked, question – from the perspective of a historical novice – in accounts of nation building. Perhaps throughout time, but specifically in the nineteenth century, people of different racial and ethnic groups had sex with each other, sometimes willingly and sometimes not, and many even married. The story that Lim provides of how these daily life blurrings of racial boundaries resulted in a ‘thicker border between white and non-white El Paso’ due to the actions of elites who ‘sought to erase the realities of multiracial life in the borderlands’ is especially instructive to our current historical moment (p. 93). As those of us living in the United States today question the ‘America’ invoked by the slogan ‘Make America Great Again’, Lim's insights remind us that anything that is not a multicultural rendering of our history is a story of elite nation-building processes.

Indeed, while reading Lim's fascinating account, the phrase ‘everything old is new again’ played on ‘repeat’ in the back of my mind, as when Lim points out that in 1929 a new immigration law criminalised entry without inspection (p. 172). (This is exactly the change the Trump administration implemented in the spring of 2018 that led to the incarceration of parents and their separation from their children.) The phrase is the title of a piece published in 1997 in the International Migration Review, in which authors Josh DeWind and Philip Kasinitz made this useful observation about then current immigration public policy debates:

They go on to suggest: ‘one important role that social science can play in this debate is to clarify assumptions about the past’ (p. 1097). Lim's work does just this.

By offering a detailed and fascinating historical account of the borderlands in the period from 1880 to 1930, Lim, as the best social scientists do, tells stories relevant to those of us living a hundred years later, at the end of what we will likely come to consider to be a similarly important historical period of nation-building, 1980–2030. We live at a time marked by globalisation, where new technologies – albeit smartphones rather than the railways Lim writes of – connect populations and enable mobility in ways previously unimagined. And so, today – every day – belonging is under negotiation; we – in the United States, but also in Europe and other countries around the globe – question who is included and who is excluded from our national imaginaries. Lim's work reminds us to pay close attention to who is visible and invisible in these debates, and specifically to the way elites in power respond to the mobilities of marginalised citizens. Perhaps if we do, we can create public policies that include mobile individuals rather than exclude and silence them.