In 1850, after three decades of political turmoil, Portugal started investing in major public works, particularly, in the construction of a national railway network. This strategy followed closely the suggestions of the Saint-Simonian technocrats with whom Portuguese engineers had been engaging since the 1820s. Additionally, it came in response to the longtime neglect suffered by the Portuguese transportation system, which hindered communications and trade between different areas of the kingdom and with neighboring Spain. The main goal of the investment was to modernize the national transport system, attract to Portuguese harbors a large portion of the traffic between Europe, Africa, and America, and, in general terms, put the nation on the path of progress. By the end of the nineteenth century, total mileage of the Portuguese rail network exceeded 2,300 km. This article analyzes the role of railways in the improvement of communications between the Portuguese provinces, their appropriation in a unified nation-state, the degree of integration of the Portuguese economy with the Spanish and European economies, and the construction/reinvention of Portugal as a modern and technological nation. To achieve these goals, I will use three key concepts: territorial appropriation, circulation, and globalization. Sources include statistics of railway operation and previous works analyzing the impact of railways on the Portuguese transport system and economy, the outcomes of operating transnational lines, and the importance of technology for the reinvention of Portugal during the second half of the nineteenth century.