In a thorough, analytical study that brings together urban history and the history of the state, Simón Castillo Fernández argues that the canalization of the Mapocho River alongside central Santiago, and the construction of parks and new streets that went along with it, was “the principal urban design project [la principal operación urbanística] in Santiago between 1885 and 1918” (p. 435); he further argues that this project was the first in which “the State . . . used all its available tools to intervene in the urban landscape” (pp. 435–36). This project, he argues, expanded the core area of the city by adding not only the formerly peripheral Mapocho and its banks but also large areas on the north side of the river. Much as Benjamín Vicuña Mackenna had brought the rocky Cerro Santa Lucía into the east side of the central city by building an elaborate park on it in the 1870s, the Mapocho project took a strip of garbage dumps, gravel pits, and — not least — settlements of poor people and made it into a corridor of restrained river, formal parks, monumental public buildings, and more or less orderly new streets. This extension eventually reached Cerro San Cristóbal and led to the designation of that small mountain, with its emblematic 1904 statue of the Virgin Mary, as a huge public park to be clothed in irrigated forest.This 35-year transformation made at least a gesture toward most of the major goals of urban design and reform in those years: speeding up traffic, constructing imposing streets and buildings, removing garbage dumps, improving sewers, enforcing sanitation rules, reducing natural dangers such as floods and human dangers such as crime and alcoholism. The ongoing debate over poverty and the meaning of citizenship was ever present; leaders of the city and the project expressed sympathy for the miserable living conditions of the poor while working to eject them from the expanding central city. The river itself also played a role in the story, as the city, the state, and private investors sparred over the use of its waters for drinking and irrigation, the disposal of trash and sewage, and even the extraction of sand and gravel for building materials.Castillo Fernández tells his story with clarity, thoroughness, and ample evidence. He uses many documents from the Intendencia de Santiago (the branch of the central government responsible for the city), the Municipalidad de Santiago (the local government), the Ministerio de Industria y Obras Públicas (home of the state's engineers and administrator of state public-works projects), and the property records of the Conservador de Bienes Raíces; a variety of published national and municipal documents; and key books and other publications from hygienists, planners, engineers, and assorted experts. The rise of engineers and other professionals in the urban projects and state activities of late nineteenth-century Chile makes this last category of sources particularly useful for understanding the changing notions of city life and the role of the state.The many illustrations, especially the period photographs, really do illustrate many important points about the development of the banks of the Mapocho that would not be nearly so easy to grasp from prose alone. Exceptionally informative captions direct the reader to key features and tie the illustrations into the analysis of class, aesthetics, density, and land use. The many plans and maps of small areas help show the changes in the portrayal, ownership, use, and topography of the Mapocho. There is one minor omission: readers who want to follow the descriptions of streets in detail may want to find a clearly legible map of central Santiago, which the book unfortunately does not contain. The book's main argument does not depend on the details of street corners, but Castillo Fernández's thoroughness and attention to detail means that he does mention many precise locations, giving both historical and present-day names. I know that part of Santiago fairly well, but I sometimes found myself trying to remember, more or less, whether Calle Estado is east or west of the Mercado Central.In addition to its valuable contribution to the history of Santiago and of urban public works generally, this book joins Sol Serrano's ¿Qué hacer con Dios en la República? (2008) and Thomas Miller Klubock's La Frontera: Forests and Ecological Conflict in Chile's Frontier Territory (2014) among important recent studies that help us to understand how urban projects and municipal issues contributed to changing the small, Weberian state of the early national period into the “modern” state characterized by economic intervention, public works, safety regulations, and the like.