Rail Line along CA coast thru Loleta and Eureka - RAILROAD.NET -- that's the north end of the former Northwest Pacific line. I'd earlier traced it with Google Maps
From a link in that thread, I found
The Great Redwood Trail Agency which is turning most of the former NWP line into a trail.
The Great Redwood Trail is a 320-mile, world-class, multi-use rail-to-trail project connecting California’s San Francisco and Humboldt Bays. The legacy trail will travel through some of the wildest and most scenic landscapes in the United States, traversing old growth redwood forests, running alongside oak woodlands and vineyards, and winding through the magnificent Eel River Canyon.
Much of it is now done, and work continues on the remaining parts of it.
Along the active SMART line itself, this trail is being built:
Multi-Purpose Pathway | Sonoma-Marin Area Rail Transit
The Sonoma-Marin Area Rail Transit (SMART) District along with partner agencies have constructed over 28 miles of pathway, of which approximately 21 miles are Class I SMART Pathway within and along the railroad right-of-way.
Currently, 9.5 miles of pathway are slated for construction in 2023/2024. SMART is advancing another 31 miles of planned pathway through design, of which 3.5 miles are already fully funded for construction.