Eminönü is one of the oldest neighborhoods of Istanbul, located in the center of Old City area. Until April 2008, it used to be one of the 32 main districts of the city but with a new regulation in city planning now there are 39 districts and Eminonu is not one of them anymore, it's just a neighborhood today within Fatih district. Being at the entrance of the Golden Horn, the old harbor next to the Sea of Marmara, Eminönü was always an important site since the Byzantine times until today, it was the hub of ancient Constantinople. The city started to grow from this point, thus some of the oldest neighborhoods are located near Eminonu today: Sultanahmet, Sirkeci, Karaköy, Süleymaniye, Cagaloglu, Cemberlitas, Beyazit, Kumkapi, and so on.
During the late Ottoman period, a big train station where the Orient Express used to come and other impressive stone buildings such as Post Office were built in the area. Eminönü continued to be a busy center throught these ages as well.
During the Republic period, roads were widened, a large square was opened, Galata bridge was replaced with a bigger one, Spice market was re-organized, and a tram line was built. Today, Eminönü is one of the busiest neighborhoods of Istanbul and it attracts lots of tourists and local people to its bazaars and other historic sites. It has only 55,000 residents but during the day time it goes up to 2 million people.
The name of the neighborhood comes from Ottoman period, when there were many Maritime Customs and the Customs Superintendent offices (Emin in Turkish) in the neighborhood. And "önü" means "in front of", so this was a neighborhood of courts and customs.