Tom,
I took the OP as meaning in California primarily, although possibly Nevada, OR or WA?
Yeah, go to Colorado and the picture changes, but not much after the 1920s. The last place where there was direct interchange -- other than DRGW/RGS -- between NG in Colorado was between the C&S and the Rio Grande in the Leadville area IIRC. Possibly a little down at Buena Vista off the C&S Chalk Creek line (formerly to Gunnison via Alpine Tunnel, but severed). But the Rio Grande's 3rd rail between the Leadville area through Royal Gorge and into the smelters in Pueblo came up in either 1923 and 1927. At this point the Rio Grande's NG lines were gone from there, the C&S still came in from the east over Boreas Pass, but there was no way to connect to the Chalk Creek line.
Any direct C&S/DRGW NG connections in the Denver area were gone long before that. Going back further, it's more complex, but irrelevant here I suspect.
Slap my forehead moment: Of course, there was very limited interchancge between the Rio Grande and the Silverton Northern intil 1942-43, when the last of the SN's old equipment was shipped north to the WP&Y by the Army. There was some limited interchange during the 1930s, but biz was a little slow everywhere then.
I should've remembered that, I model Silverton...duh-oh
Mike Lehman
Urbana, IL
I'm sure Mike can correct me if I'm wrong, but I thought Rio grande Southern interchanged cars with the D&RGW. Except for paint schemes, many of these cars had a common origin as D&RGW designs. RGS also had some ex-C&S freight cars, so C&S designs could be justified on RGS cars. Maybe a modeler could show remnants of the old C&S lettering on a RGS car.
Farther east in Colorado, D&RGW and C&S served overlapping territory. It appears that they could have interchanged, but I don't know whether they did.
These were western railroads, but not actually on the coast, so I'm not sure whether they fit the O.P.'s perameters.
The narrow gauge East Broad Top in Pennsylvania had a practice of handling standard gauge interchanged freight cars, by putting them on temporary narrow gauge trucks; but I guess that isn't quite what the O.P. had in mind either.
Tom
FWIW, several of the lines had logging RRs that connected with them. But that's not the same as common carrier interchange.
I can't think of any offhand, but there probably was interchange where there was a connection between narrow gauge railroads of the same gauge. (not all were 3' gauge). However, unlike Colorado which had a narrow gauge system, in Washington, Oregon and California most narrow gauge railroads were isolated operations with no connections at all or ran from points on standard gauge railroads where passenger and freight were transferred.
As narrow gauge railroads were abandoned or standard gauged, their locos and cars were often sold to the railroads that were still operating as long as there was a market for them.
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I looked at the maps WA, OR & CA in American Narrow Gauge Railways by George W. Hinton. Only one map showed a connection between two narrow gauge railroads. The maps show "common carriers". They do not show railroads that were strictly industrial or logging. It looks like the Walla Walla & Columbia River interchanged with the Mill Creek Flume & Manufacturing Company. They were both standard gauged in the the early 1900's.
I tried to sell my two cents worth, but no one would give me a plug nickel for it.
I don't have a leg to stand on.
Okay so I'm new to narrow gauge... did the west coast narrow gauge railroads interchange cars among themselves? I don't mean with standard gauge railroads but actually between narrow gauge railroads themselves?
Thanks for any info...