District municipality is formed under the name İzmit, by joining town municipalities in İzmit center. In reality, after forming Kocaeli Metropolitan Municipality, establishing a municipality in the center in the İzmit' in order to survive was always in the agenda. As the result of the researches made, it was learnt that people lived in İzmit which is one of the intersections of the most important roads of the world, and the surrounding areas since 5000 BC.

İzmit was always an area of settlement until today. First Phrygians occupied the area, and later on a city was established in Basiskele location called Astakoz. With the destruction of Astakoz as the result of a earthquake, a new city called Nikomedia was established on the slopes of İzmit. In 284 BC Emperor Diokletionus declares Nikomedia as the capital. In his time, Nikomedia becomes the 4th largest city of the world after Rome, Antakya, and Alexandria. The city which faced one earthquake every century on the average, was repaired during the period of Byzantium Emperor Justinianus. However it was destroyed again. İzmit, being the last stop of Silk Road before İstanbul, was the scene to many important developments during history. İzmit, was reconstructed after conquered by Seljuks in 1078. However during the First Crusades, the city faced a terrible massacre together with İznik. The city's entering into Turkish dominancy once more was realized in the Ottoman period in 1337 and coincides with Orhan Gazi's reign. Artwork destroyed and looted during Crusades were repaired very fast. The name of the city that was 'İznikmid' was changed into 'İzmit'. Together with the development of Ottoman seamanship, İzmit ship building yard was established in Yavuz Sultan Selim period. In 1873 gulf ship cruises between İstanbul-İzmit and Haydarpafla-Ankara trains has increased the importance of the city. However the earthquake in 1894 caused serious damage. After I. World War İzmit has lost its importance, and was occupied by the British on 6 July 1920, by the Greeks on 28 April 1921 and was captured back by Turkish army on 28 June 1921. The city at one of the most important passing points with land, rail and sea transportations. 30° eastern meridian which passes from the east of İzmit is accepted as the basis for Turkey hour
(UTC+2). Main neighborhoods of İzmit district are the old towns of Saraybahçe, Bekirpaşa, Alikahya, Kuruçeşme and Akmeşle.