| YEAR | DATE | EVENT | HEAD OF STATE | |
| 1126 | Count - dinasty Wigerich | earles Sofia | ||
| 1176 | dinasty Olanda | earl Ottone I | ||
| 1208 | earl Baldovino I | |||
| 1248 | earl Ottone II | |||
| 1264 | earl Egberto I | |||
| 1311 | earl John II | |||
| 1333 | earl Simone I | |||
| 1344 | earl Ottone III | |||
| 1379 | earl Bernardo I | |||
| 1421 | dinasty Gotterwich | earl Everwin I | ||
| 1454 | earl Bernardo II | |||
| 1473 | earl Everwin II | |||
| 1530 | earl Arnoldo II | |||
| 1553 | earl everwin III | |||
| 1562 | earl Arnoldo III | |||
| 1606 | earl Adolfo | |||
| 1623 | earl Arnoldo Jobst | |||
| 1643 | earl Ernesto Guglielmo | |||
| 1693 | 26 august | earl Arnoldo Maurizio | ||
| 1701 | 29 april | earl Ermanno Federico | ||
| 1731 | earl Federico Carlo Filippo | |||
| 1803 | earl Ludovico Guglileml Gelderico Ernesto | |||
| 1817 | Principality | prince Ludovico Guglielmo Gelderico Ernesto | ||
| 1817 | prince Alessio Federico | |||
| 1854 | Prussian Administration | |||
| 1918 | Union to German State of Lower-Saxony |