To respond to various:
I doubt the San Juan would have run until the abandonment, even if it had survived the 1949-50 attempt to end it. For one thing the mail contract cited not would have lasted that long as the mail was, for the most part, taken off the trains in 1967 (contributed greatly to the end of D&RGW std. ga. pass. trains other then the CZ, which never caried mail anyway.) 2nd, road improvments in the area would have gone on in the 1951-1968 period anyway, if not quite as fast perhaps, luring the local traffic away. I doubt the tourist traffic in Summer would have gotten big enough to finance the whole year.
The D&RG(W) was down on the narrow gauge for a long time. From 1890 or so up until the WWI eara the thought was that it would all be changed to standard gauge one way or another, so why spend money on the narrow gauge? At some point getting rid of it all became the goal, presumably as the idea that getting rid of branch lines would save the railroads gained currency nationaly. After all, post 1890 the narrow gauge lines were, at best, secondary lines if not outright branches, even main lines like Salida-Grand Jct.
All of this, plus the drain on system resources represented by eastern investors demanding big dividends *now* and then followed by the WP debacle, meant that no money was spent on the narrow gauge unless it had to be and would show an improvement in profit in a very short term. even the big improvement programs of the 1920's and 1936-38 were really just catching up on things let slide for far too long, things that ought to have been done years(decades) earlier.
Bob Richardson reported on haw fast the Valley line was ripped up in '51 (last train mid-February, track gone by early March) and speculated that D&RGW was making sure that nobody could revive it.
In short, the entire corporate culture of the D&RGW saw the narrow gauge as a Bad Thing, as something that made the whole system look out-of-date, so it is no surprise that they trashed the remnants ASAP.
hank
ps In the 1970's the D&RGW was trying to find someone to buy the Silverton, hence the "running down" reffered to by one poster. Credit to D&RGW, they insisted on finding a buyer who had a plan and deep pockets instead of selling on the first offer recieved.
