SR 161 begins southwest of Eatonville and north of La Grande in rural Pierce County at an intersection with SR 7. The highway travels northeast to pass the Charles Lathrop Pack Experimental and Demonstration Forest and cross the Little Mashel River into Eatonville. The roadway crosses the Mashel River into Downtown Eatonville, turning north onto Mashell Avenue and later Washington Avenue. SR 161 turns west onto Meridian Avenue north of Eatonville High School and leaves the city on a two-lane highway. Meridian Avenue, named for a meridian parallel to the Willamette Meridian, continues north through rural Pierce County, passing Clear Lake and Tanwax Lake, before entering the community of Graham and crossing a Tacoma Rail line near Graham-Kapowsin High School. SR 161 travels north and passes South Hill and Pierce County Airport (Thun Field) before entering Puyallup. The highway turns northwest at the South Hill Mall onto 31st Avenue and intersects the SR 512 freeway in a partial cloverleaf interchange, beginning a concurrency.