Ken Montero wrote:
This "rebuilding" probably was a result of federal tax laws.
It is my understanding that, during our time period, railroads were allowed to write off (deduct) the cost of "repairs" much quicker than they could depreciate new construction (whether built in-house or by someone else) for tax purposes.
True, but this changed greatly in 1948, when the IRS considerably tightened the rules on rebuilding. You will notice that those giant rebuild and refurbish programs on most railroads faded away after 1948.