High Quality Content by WIKIPEDIA articles! Sioux City (pronounced /?su??s?ti/) is a city in Plymouth and Woodbury counties in the western part of the U.S. state of Iowa. The population was 85,013 at the 2000 census; census estimates showed a slight decline to 82,807 by 2008. Sioux City is the primary city of the four-county Sioux City, IA?NE?SD Metropolitan Statistical Area (MSA), with a population of 143,053 in 2000 and a slight increase to an estimated 143,157 in 2008. The Sioux City-Vermillion, IA-NE-SD Combined Statistical Area has an estimated population of 156,762 as of 2008 It is the county seat of Woodbury County,[4] in which the large majority of the city lies.