Built between 1927 and 1938 to connect the Caspian Sea and the Persian Gulf via Tehran, the Trans-Iranian Railway is often associated with the reign of Reza Shah Pahlavi (r. 1925-41) and his nation-building project. However, it was during the Allied occupation of Iran (1941-45) that rail transport capacity drastically increased as the Allied forces expanded the railway system to transport lend-lease materials to the Soviet Union. Concurrently, the Allies restricted civilian use of Iran’s highways to prioritize wartime needs. These developments during the early 1940s shifted travel routes and created a situation in which Iranian travelers relied heavily on the Trans-Iranian Railway for vacation, tourism, and pilgrimage. Particularly remarkable was the surge of pilgrimage traffic not only to Qom but also to holy cities outside of Iran such as Najaf, Karbala, and Mecca by Shi’i travelers who combined rail transport with boats, cars, and caravans. This study examines how these travelers experienced measures that regulated the flow of movement by Iranian and Iraqi state authorities as they tried to visit the holy cities. Iranian historiography views transborder movement primarily through the anxieties expressed in Tehran-centered nationalist discourse, giving scant attention to travelers’ experience of such movement. Yet, the case of the Trans-Iranian Railway in the 1940s deserves attention because it illustrates how a purportedly national infrastructural project facilitated the formation of an informal transnational infrastructural network, producing possibilities for multi-scalar spatial movement for travelers. Using the Iranian press, memoirs, and American and British archival materials, this paper suggests that mobilities produced by the Trans-Iranian Railway were conducive to both a heterogeneous national community and transnational possibilities. Iranian pilgrims shared the experience of traveling in the crowded railway space, being stuck in border towns, taking advantage of the human smuggling rings to cross borders, and facing various forms of discriminations on account of being Shi’is/Iranians. Moreover, they shared the same transnational infrastructural network with communists who traveled between Moscow and Baghdad via Tehran and Khorramshahr. Such shared experience of movement left room for travelers to become not only Iranians but also Khuzestanis, Shi’is, communists, or possibly all of these at the same time.