Iron Horse Imperialism tells the story of a railroad that took almost half a century to be completed, and for this reason held a very complex and changing relationship with various governments belonging to different political regimes, going from the Porfiriato to the Revolution and the post-revolutionary state. Even though some research has been done on the Southern Pacific of Mexico (SPM), the novelty of this book is twofold: first, that it deals with a longer period, covering the particularly troublesome decades of the 1910s and 1920s; and second, that it makes use of archival sources that had not been explored so far, particularly the corporate records of the company, kept at the Huntington Library in San Marino, California.

The SPM was born as the Sonora Railroad, built between 1880 and 1882 from the US frontier in Nogales to the Pacific port of Guaymas. The idea of extending the line to the south, in order to connect in Guadalajara with the rest of the Mexican railroad system, arose in the late 1890s, but started to materialise only in 1905. Construction works continued until 1912 from both sides of the line, but were suspended due to the revolutionary turmoil before the most technically challenging section of 160 kilometres crossing the Sierra Madre Occidental could be laid. It took 11 years and a new agreement with the government for the works to be reassumed, and an additional four-year span for the line to be finished in its entirety, being inaugurated in 1927. In 1951 the company was sold to the Mexican government, and eventually became a part of the National Railways of Mexico (NRM).

The author inquires about a double paradox: on the one hand, a business enterprise that had a very limited profitability from the beginning (it only paid dividends in five of the 70 years of its operation as a private concern) and yet did not give up in its efforts to extend its line or make costly investments looking for a more efficient operation; on the other, a government that welcomed foreign resources while at the same time trying to strengthen its national economy and its political system. In the very long period during which the line was being laid, the components of these two issues also changed, generating new tensions as the company put a limit to its endeavours and the government became more nationalistic. The railroad's situation was even more complex, as it had to deal with social and cultural aspects stemming from labour relations and from its insertion into a region that was both peculiar in its demographic traits and isolated from central Mexico.

An important issue has to do with the legal status of the company relating to its nationality. This matter should have been solved by the railroad law, which summarised the terms in which all the concessions to foreign enterprises during the Porfiriato were granted. Those regulations included a clause that stated: ‘The company will always be Mexican, even though it had been organized abroad and all or some of its members were foreigners’ (Article 49, 1899 Railroad Law). However, there seems to have been a permanent ambivalence – held by the company as well as by the government after the revolution – with respect to the company's nationality. Whenever there was a motive of pride, SPM's parent company (the Southern Pacific Railroad) and the press proclaimed it a US concern; when it needed to negotiate with the government, SPM identified itself as legally Mexican. As for the government, when it wanted the company to obey the Mexican legislation, it recognised its Mexican legal status; when it was asked to grant the company equal rights, it apparently denied the latter full recognition as a Mexican corporation (p. 135).

This leads to a more general issue, namely the varying relationship between the company and the Mexican government throughout the period. While Díaz dispensed toward foreign companies stable and predictable treatment, the revolutionary governments, starting with that of Venustiano Carranza, wavered between indifference, ambivalence and outright discrimination. According to the author, in matters related to reparations from damages inflicted during the revolution and the Cristero rebellion, to taxes or to labour issues, the government showed its preference for the state-controlled railroads, the NRM. At the same time, some of the company's policies – like those that discriminated against Mexican workers – were at odds with the growing nationalism of the regime, showing that it had not fully understood its position in Mexico or the way in which the political environment had evolved.

There are several misunderstandings in the narrative that deserve to be clarified. One is the idea that the Díaz regime discriminated against Mexican railroad companies while it favoured those of foreign origin, something that, apparently, the revolutionary governments simply turned upside down. This was hardly the case. First, there were very few railroads built by domestic companies throughout this period; second, there is no proof that there was a differential treatment against them by the Porfirian administration. What is true is that once the government put the NRM under its direct control, those companies that remained independent received increasingly disadvantageous treatment. There is also confusion about the starting of Mexico's oil exports – not in the 1880s, as stated here (p. 25), but the 1910s) – and about the contents of Article 123 (pp. 56, 58). And although some interesting issues are portrayed in this work, I feel it could have provided a deeper analysis of the company's performance and of its role in the regional economy.

Finally, the book confirms an intriguing aspect about Mexico's railroad history. As happened with other railroad companies in Mexico, the SPM made a significant contribution to the country (by means of integrating the western coast into the rest of the territory, offering fast and cheap transportation, and providing an exit – to the internal as well as the external markets – for the flourishing regional production of fruits an vegetables) but was far less successful from an entrepreneurial point of view.