Introduction

Abstract Between 1870 and 2020, Europe’s territorial development was shaped by border shifts, state formation, and regional integration. Understanding these changes requires both theoretical models and empirical, spatially precise data. Regional European Geographic Information System (REGIS) addresses previous gaps in historical GIS by providing detailed, consistent digital maps of administrative boundaries over time. It enables the analysis of long-term regional trends despite varying national border changes, using census data as a key reference. The database supports comparative and diachronic studies across Europe and facilitates integration of socioeconomic indicators into historical maps. However, full spatial–temporal continuity remains challenging, especially at the municipal level. REGIS thus lays the groundwork for future historical GIS development and promotes interdisciplinary research into Europe's territorial, demographic, and economic history.