Portland is the largest city in the U.S. state of Oregon and the seat of Multnomah County. It is a major port in the Willamette Valley region of the Pacific Northwest, at the confluence of the Willamette and Columbia Rivers. The city covers 145 square miles (380 square kilometers) and had an estimated population of 639,863 in 2016, making it the 26th most populous city in the United States. Approximately 2,424,955 people live in the Portland metropolitan statistical area (MSA), the 25th most populous MSA in the United States. Its Combined Statistical Area (CSA) ranks 18th with a population of 3,160,488. Roughly 60% of Oregon's population resides within the Portland metropolitan area.