Sanjak of Kocaeli
Kocaeli derives its name from Akça Khodja, an Ottoman Turkish warleader who began the conquest of the region from the Byzantine Empire. His domain (in Turkish Koca-ili or Koca-eli, "land of the Khodja") was recognized as a sanjak, with seat at Iznikmid (Nicomedia, modern Izmit) already in 1329, making it one of the earliest sanjaks of the Ottoman Empire. With the establishment of the Anatolia Eyalet it became part of it until 1533, when it was added to the newly created Eyalet of the Archipelago.
It remained part of the Eyalet of the Archipelago until the Tanzimat reforms of the 19th century; by 1846, it had been transferred to the Kastamonu Eyalet. In 1855 it passed to Hüdavendigâr Eyalet (and its successor Hüdavendigâr Vilayet after 1867). From there it was transferred to the Istanbul Vilayet in 1870, before returning briefly to Hüdavendigâr (1871), becoming an independent sanjak in 1872, and returning to Istanbul in 1876. In 1887, the Sanjak of Kocaeli (increasingly known as Izmid, after its capital) returned to the jurisdiction of the Hüdavendigâr Vilayet.
- Birken, Andreas (1976). Die Provinzen des Osmanischen Reiches. Beihefte zum Tübinger Atlas des Vorderen Orients (in German). 13. Reichert. ISBN 9783920153568.