The purpose of this thesis is to study the earliest recorded history of the Cowlitz River corridor, focusing on early exploration and settlement. The importance of the corridor as a major transportation route linking Puget Sound to the north and the Columbia Willamette waterways to the south is emphasized with primary source observations. The study is based on both primary and secondary source materials housed in libraries throughout the Pacific Northwest and Canada. Among the sources include letters, journals, federal documents, periodicals, articles, drawings and monographs.