With particular focus on the North Pacific Coast Railroad and their narrow gauge line from Sausalito to the Russian River.
The following gives a picture of the comings and goings of the railroads around Marin. 

NOTES:
The abbreviation "ng" indicates a narrow gauge line with tracks 3’-0" between rails. 
The abbreviation "sg" indicates a standard gauge line with tracks 4’-8.5" between rails (from old wagon days). 

Generally, the Northwestern Pacific Railroad lineage in Marin stems from two distinct lines: the North Pacific Coast Railroad which became the North Shore Railroad, and the San Francisco and North Pacific Railroad. They were merged in a deal by Southern Pacific and Santa Fe in 1907.

 
• 03/ 21/ 1870: San Rafael & San Quentin Railroad builds first rail line in Marin. (sg).
• 12/ 16/ 1871: North Pacific Coast Railroad founded and incorporated. (ng)
• 03/ 1873: NPC construction begins. (ng)
• 07/ 25/ 1874: NPC rails reach San Rafael from "Saucelito." (ng)
• 01/ 11/ 1875: NPC begins regular service to Tomales. (ng)
• 03/ 11/ 1875: SR&QR leased by NPC for 43 years. (changed to ng, 4/10/1875)
• 09/ 1876: NPC reaches Russian River at Monte Rio. (ng)
• 07/ 15/ 1877: NPC begins passenger service to Duncan Mills (Russian R.). (ng)
• 02/ 19/ 1884: NPC sends first train through Corte Madera tunnel. (ng)
• 04/ 26/ 1884: Strawberry Point/Alto Hill route abandoned. (ng)
• 04/ 11/ 1886: NPC begins regular passenger service to Cazadero. (ng)
• 03/ 17/ 1890: NPC begins regular service into Mill Valley.
• 03/ 07/ 1902: NPC sold and renamed North Shore Railroad.
• 1902 to 1903: North Shore converts southern Marin suburban lines to standard gauge with novel electric "third rail" design (no overhead wires) for commuter service from Sausalito to Fairfax and San Rafael via San Anselmo. (sg)
• 12/ 04/ 1904: NS opens Bothin Tunnel under White’s Hill. White’s Hill route abandoned.
• 01/ 08/ 1907: Marin railroads reorganized in a Southern Pacific/Santa Fe partnership and renamed Northwestern Pacific (There was another Marin line besides the North Shore (formerly NPC): Originally it was called the Sonoma and Marin Railroad when started south from Petaluma in 1874; Peter Donahue assimilated the S&M into his Sonoma-area San Francisco and North Pacific Railroad in 1876. His SF&NP reached San Rafael in 1879, and Tiburon by April 1884; The SF&NP was re-organized as the California Northwestern Railroad in 1893. Scenic railways such as the Mt. Tamalpais and Muir Woods Scenic Railway [1896 to 1930] were not included).
• 1908 or 1911: NWP adds third-rail electric commuter service from Fairfax to Manor.
• 1909: Sausalito becomes the exclusive terminal for passenger trains; Tiburon becomes the exclusive terminal for freight trains.
• 04/ 01/ 1909: NWP builds a southern connection between the two once-rivals from Baltimore Park to Detour (near MMWD office)
• 11/ 15/ 1909: NWP standard gauge trains reach Duncan Mills via Santa Rosa. The popular "Triangle Trip" including the Point Reyes leg commences. (sg and ng)
• 10/ 23/ 1914: NWP drives Golden Spike at Cain Rock (east of Garberville) connecting Sausalito and Eureka by rail. (sg)
• 1920: NWP extends standard gauge from Manor (Fairfax) to Pt. Reyes Station. Abandons narrow gauge service from Sausalito to Pt. Reyes Station.
• 1920s: Auto and truck use starts to increase rapidly. Train use begins to decline likewise.
• 1926: NWP track between Duncan Mills and Cazadero standard-gauged.
• 1929: Santa Fe sells its interest in the NWP to Southern Pacific.
• 1929: Concrete highway, Sir Francis Drake Blvd., built to Point Reyes Station.
• 03/ 30/ 1930: Last scheduled narrow gauge train heads to Point Reyes Station. Tracks between Point Reyes and Monte Rio abandoned completely.
• 08/ 01/ 1933: Track abandoned from Duncan Mills to Cazadero.
• 08/ 01/ 1933: Track abandoned from Manor to Point Reyes Station.
• 11/ 15/ 1935: Russian River line from Santa Rosa abandoned. (sg)
• 03/ 01/ 1941: Marin suburban service discontinued along with the remaining Marin-San Francisco ferry service. (sg)
• 11/ 23/ 1941: Southern terminal for Eureka passenger service shifts from Sausalito to San Rafael. (sg)
• 1942: All track from Larkspur to Manor (Fairfax) and to San Rafael via San Anselmo abandoned.
• 05/ 01/ 1955: Almonte to Mill Valley spur abandoned.
• 11/ 09/ 1958: Passenger service to Eureka terminated. Eighty Eight years of Marin passenger service comes to an end. (sg)
• 07/ 20/ 1961: Puerto Suello Tunnel (San Rafael, north) destroyed by fire. Tunnel closed for many years; finishes off freight service.