1958-60: "The lookout construction work is performed by the Department's own carpentry crew. In the past two years, the crew completed nine lookouts at a cost averaging $8,000 apiece, one of which is located at Green Knob, Clark County." (2nd Biennial Report Washington Department of Natural Resources)
August 18, 1969: Green Knob is one of five lookouts in the Battle Ground district to be discontinued and disposed of after being replaced by air patrol. Plans to move this tower to the DNR District Headquarters, the tower shortened from 40' to 10' and the cab rebuilt as an interpretive center. (The Oregonian)
National Geodetic Survey
DESIGNATION - GREEN KNOB LOT PID - RD4382 STATE/COUNTY- WA/CLARK COUNTRY - US USGS QUAD - YALE DAM (1993)
DESCRIBED BY US GEOLOGICAL SURVEY 1953 LOCATED ABOUT 9.1 MI E. OF AMBOY, 7.6 MI NE. OF YACOLT. ON HILLTOP KNOWN AS GREEN KNOB.
TO REACH FROM YACOLT, DRIVE 5.0 MI E. ON GRAVEL RD. TO RD. FORKS. TAKE LEFT FORK 6.4 MI TO RD. FORKS. TAKE LEFT FORK 3.55 MI TO SHARP RIGHT TURN AT SIGN GREEN KNOB LO. TURN SHARP RIGHT FOLLOWING RD. 1.35 MI TO LOT AND STATION.