Klamath is an unincorporated community in Del Norte County, California, situated on US Route 101 inland from the mouth of the Klamath River. The population of Klamath is 632 based on US Census estimates, down from 779 recorded in the 2010 US census. For statistical purposes, the United States Census Bureau has defined Klamath as a census-designated …Klamath is an unincorporated community in Del Norte County, California, situated on US Route 101 inland from the mouth of the Klamath River. The population of Klamath is 632 based on US Census estimates, down from 779 recorded in the 2010 US census. For statistical purposes, the United States Census Bureau has defined Klamath as a census-designated place. Klamath is at an elevation of 30 feet. Klamath is located within the Yurok Indian Reservation.