Ketchikan is a city in Ketchikan Gateway Borough, Alaska, United States, and the southeasternmost sizable city in that state. With an estimated population of 7,368 in 2007, it is the fifth most populous city in the state. Ketchikan's economy is based upon tourism and fishing, and the city is known as the "Salmon Capital of the World. " The Misty Fjords National Monument is one of the area's major attractions. Ketchikan is named after Ketchikan Creek, which flows through the town. Ketchikan comes from the Tlingit name for the creek, Kitschk-hin, the meaning of which is unclear. It may mean "the river belonging to Kitschk"; other accounts claim it means "Thundering Wings of an Eagle. " Ketchikan's secondary post office box zip code, 99950, is the highest zip code ever assigned in the United States. Most residents use the zip code 99901. The lower end of the U.S. ZIP Code system is in the town of Agawam, MA, with its reservation defined at 01001. Ketchikan also has the world's largest collection of standing totem poles, located at three major locations: Saxman Village, Totem Bight, and the Totem Heritage Center.