While I'm obviously not aware of what the codes in place were in 1937, the American Concrete Institute (ACI) has been around since 1906 I believe. In addition,

While I'm obviously not aware of what the codes in place were in 1937, the American Concrete Institute (ACI) has been around since 1906 I believe. In addition, my comment is not in response to whether or not the building codes or inspectors back then knew what we now know about concrete (they obviously did not), my comment is in response to a modern day visitor like the post's author looking at something with a relatively straightforward explanation using today's engineering principles and calling it magic.