Source: 1915 USGS Mt. Rainier NP topographic map
The Grindstone Trail was the original trail from Wilkerson to Mowich Lake, originally named Crater Lake since it resembled a lake in a volcano. The trail was built from 1881-83 when Bailey Willis, geologist for the Northern Pacific Railroad, was sent to explore the northwest area of Mt. Rainier for potential development for tourism.
Bailey Willis developed the Grindstone Trail to Mowich Lake, later building a 4-building camp 4 miles west of the NP boundary, and then extended the trail to Spray Park and eventually the Carbon River and Carbon Glacier. He also helped develop the Carbon River Trail from the meeting of the Grindstone Trail where it crossed the Carbon River 3 miles north of Fairfax where the highway 165 bridge currently crosses the river, up the Carbon River to the junction with the Grindstone trail at the confluence of Cataract Creek and the Carbon River.
These trails were used in the expedition by USGS geologists in 1896, tasked with the work to explore and document the geology and glaciers of the northern half of Mt. Rainier. Their work, published in the 1898 Annual Report of the USGS, was a cornerstone of the material used to designate Mt. Rainier a national Park.
The only remaining part of the Grindstone Trail is in the NP in the last 2 miles to the Mowich Lake Campground, a 1 1/4 mile trail from the bend in the road at the head of the meadows, crossing the road three times to the road on the far west side of Mowich Lake, see "Pack Trail" on 1971 map below. All the rest of the Grindstone Trail is highway 165 or lost to history.
The Carbon River trail is also lost to history as floods and the NP has changed the routes of trails in the Carbon River Valley over the decades and the Carbon River road from the junction of highway 165 to the NP entrance is on the south side of the river, where the trail followed the north side where little of it is known or still exists.
Just thought you'd like to know some history. And the 1915 USGS topographic map is a high resolution digital image of an original print of the 1915 USGS topographic map of the NP which was surveyed 1910-13. The image is from an original print of the map in the Bailey Willis collection at the Huntington Library in Los Angeles.