I saw the address on some of the early printed material (but not the super early material) was in Seattle: 9050 Empire Way South. Empire Way was named for “Empire builder” James J. Hill, the railroad king who built the line over Stevens Pass to Seattle from Chicago in 1893. Around 1983, Empire Way was renamed by the city council to Martin Luther King Jr. Way. The building at that location is here. I wonder if that's the old Warn factory?