"Grand Scale Railroads" is a term meaning toy trains with gauges from 12" to 24". The fabled Hoosgow and Mukluk (vida infra) is only one of a number of Grand Scale Railroads in Northern California, although it certainly is the worst! Next door the the H&M is the 15" gauge Glenwood, South Park and Pacific (the oldest in the Santa Cruz mountains). At Davenport, on the coast north of Santa Cruz, is the 19" gauge Swanton Pacific. It contains the remaining operating equipment from Louie McDermot's 1913 Overfair Railroad. The Billy Jones Railroad is 18" gauge and runs regularly in Los Gatos.
If you want a railroad around the house, look at the Emeral Hills Ry in Redwood City.
Up north, in Tilden Park overlooking Berkely is the 15" railroad in America, the Redwood Valley Railway. Built by the late Eric Thompson, it remains at the top of the heap of Grand Scale Trains. Moving north to Sonoma, we find Sonoma Train Town, another 15" commercial operation with probably the most extensive landscaping of all.
Eric Thompson began his operation with a 12" gauge locomotive which was running at Folsom, but its present status is unknown. Farther north and east is the Orland, Newville and Pacific Railroad at Orland, CA. East to the Sierra Foothills was the 12" gauge Sonora Shortline at Tuolumne, but no longer on the web. Not far away is a private operation called the Hetch Hetchy & Yosemite Valley, which is extensive but private.
Up north near Redding are three more, the B.A.D. Great Northern, the Nickel Plate Railroad, and the Trinity Alps Railroad.
Going to central California is the Hillcrest & Wahtoke RR. Sean will also sell you anything you need to build your own Grand Scale railroad, or he will build it for you. Farther south is the Joshua Tree & Southern, a really serious railroad club in the desert.
Here are some photos from three of these pikes and some links to some others:
Pictures of the Glenwood, South Park, and Pacific
Pictures of the Hetch Hetchy & Yosemite Valley
Pictures of the Hoosegow and Mukluk
The Billy Jones Wildcat Railroad
The Swanton Pacific
The Emerald Hills Ry
Sonoma Train Town
The Orland, Newville & Pacific
The B.A.D. Great Northern Ry
The Nickel Plate Railroad
The Trinity Alps Railroad
The Hillcrest & Wahtoke RR
The Joshua Tree & Southern
If these pictures make you want to build you own Grand Scale Railroad, here is a source for some very reasonably priced castings to get started: GrandScaleParts.com