Prehistorical and Nikomedian era
Kocaeli, which is located at the intersection of import and land and railway routes between the Asian and European continents, is one of the most important industrial establishments of the Marmara Region as well as our country today. The history of Kocaeli dates back to ancient times. The first cities established in the region called Bithynia were named as Olbia, Astakos, Nicomedia, iznikmid, izmid, izmit and Kocaeli respectively. Megarians from Thrace settled in the district of Basiskele located in the southern side of izmit Bay in 712 BC and established a city named Astakos. The people of Astakos settled in the area where izmit is located today in 262 BC. This city was named as Nicomedia afterthe founder of the Bythinian Kingdom and it remained as the capital of the kingdom until it was destroyed.
Roman Emperor Diocletian invaded Nicomedia in 284 and declared it the capital of the Roman Empire. The city became the fourth greatest city of the world during this era. However, Nicomedia lost its importance after istanbul was declared the capital by Emperor Constantine and the road between Kadikoy and izmit was closed down by Emperor Justinianus due to military reasons and transportation shifted to iznik.
Kocaeli was firstly captured by the Turks during the Seljuk era in the late 11th century . After iznik was declared the capital of the Anatolian Seljuk Empire, the city became far more important. However, the city which was invaded by the Crusader commander Aleksios Comnenos for a short time during the Crusades went under absolute control of the Turks during the era of Orhan Bey. There are few historical buildings that descended from the Seljuk era to today because of the looting carried out by the Crusaders.
Kocaeli was made a part of the Ottoman territory by Akcakoca, a margrave of Orhan, the son of Osman, in 1337. Nicomedia was named firstly iznikmid, then izmid [izmit] after going under Ottoman control. The social and commercial life of Kocaeli regained vibrance after the railway which ran between istanbul and izmit in the 19th century and also ran between Haydarpasa and Ankara starting from 1873 reached the city. The city became an independent district in 1888 and its name was changed into Akcakoca which means "the home of Akcakoca".
Kocaeli, which lost its significance for a certain period of time due to the destruction and problems emerging as a consequence of World War I for some time and occupied first by the English [July 6th, 1920] and then by the Greek [April 28th, 1921] was liberated from the occupation by the Turkish armyon June 28th, 1921. Kocaeli has 12 districts which are Basiskele, Darlca, Dilovasl, Cayirova, lzmit, Derince, Gebze, Golclik, Karamlirsel, Kandira, Kartepe and Korfez. After the declaration of the Republic, Kocaeli became one of the most rapidly developing provinces of our country in terms of industrialization. The prime reason to this is its being located in close distance to istanbul and its wide variety of transportation possibilities. In 1936, izmit Paper Factory which was the first paper manufacturing factory was opened and it was followed by the second cellulose and paperfactory in 1944. SEKAfacilities were expanded in 1954, 1957 and 1959 respectively thus making Kocaeli a high level industrial area of Turkey after a rapid process of industrialization which continued on to today. Another important fact about Kocaeli is that all Turkey adjusts its time according to Kocaeli as the 300 meridian passes through the highway crossroads bridhe in Kosekoy.