A neat story that I had not heard of before.  I found some additional on-line and photos information. 

The history of the telescope can be found at: http://www.astro.caltech.edu/palomar/about/history.html

The mirror blank was cast by Corning Glass Works in Pyrex, which was new at the time.  The first attempt at pouring the mirror occurred in March 1934, with great fanfare, and it failed.  That mirror is apparently on display at Corning.  The second attempt, done quietly on December 2, 1934, was successful.  The blank was annealed for 10 months and the oven was opened on October 25, 1935.  On March 25, 1936, the blank was loaded onto NYC S-499010 and departed for CalTech. There are reports that the train’s speed limit was 25 mph 

See http://www.journeytopalomar.org/palomar.html for a video showing the loading of the mirror onto the flat car and the train in motion, as well as the impact of the mirror as it traveled across the country.  Note that the video is an archaic Quick Time format and so you may need to download or tweak some of your computer’s tools.

See: http://www.truckinginfo.com/blog/trailer-talk/story/2015/06/a-fruehauf-lowboy-carried-palomar-s-precision-mirror-back-in-1947.aspx for a description of the move.

From conception to completion, this project took 20 years!  So the next time you hear someone complaining about science not producing results instantly, think about the dedication of the folks who saw this project through.