This article addresses the intertwined development of the port cities of Rotterdam and Antwerp into border zones that took place with the upswing of steam navigation in the upcoming age of high mobility. It focuses on administrative practice, namely local authorities' approaches to identifying and registering mobile people, to shed new light on the often-presumed shift in migration control in this period. Scrutiny of the paperwork used and produced by local authorities tasked with migration control suggests that administrative practice does not fit into coherent narratives of high modernity characterised by the increasing relevance of nationality, border control management, and a growing impact of the nation-state. Instead, this era is characterised by the layering of control practices: Resilient practices-some dating back to pre-modern times, some lacking coherence; the practices of individual police agents; and national policies.