Porter County is a county in the U.S. state of Indiana. As of 2020, the population was 173,215, making it the 10th most populous county in Indiana. The county seat is Valparaiso. The county is part of Northwest Indiana, as well as the Chicago metropolitan area. Porter County is the site of much of the Indiana Dunes, an area of ecological significance. The Hour Glass Museum in Ogden Dunes documents the region's ecological significance.