The STH 57 project existing highway and proposed design route traverses predominantly upland portions of the Door Peninsula paralleling the Green Bay shoreline in Brown and Kewaunee Counties. In Door County the project area turns east, heading inland across the uplands toward Sturgeon Bay. In Brown and Kewaunee Counties the project area follows the crest of the Niagara Escarpment, and the dolostone bedrock is relatively close to the ground surface. Glaciation and inundation by Glacial Lake Oshkosh have produced level to gently rolling topography.
In Door County, the dolostone bedrock outcrops at Brussels Hill, but is buried under level to rolling glacial deposits in much of the project area. The near surface bedrock and recent glaciation have produced a poorly drained landscape with extensive wetlands and sluggish streams and rivers. Creeks in Brown County have waterfalls where they cross over the edge of the escarpment. Some cherty dolostone bedrock exposures may have served as lithic source areas for prehistoric peoples. Cherts were also present in the glacial gravels of the region. Along Green Bay from Dyckesville to the north, bedrock is not evident and the substrate consists of glacial and post-glacial lake terraces which have been wave cut in places. Soils in these areas are dominated by sand and red clay.