This is perhaps a bit soft question but when did signal processing become a field of its own? It would appear to have first been a branch of mathematics and statistics but then emerged as an independent field.
If there is any book that would cover this, or perhaps some special issue article, I would love to read it.
PS. Please help to add relevant tags; I could not find any
There's a nice historical account given by the IEEE Signal Processing Society, that references 1948 as the year the field began. I'm not sure if that's necessarily accepted as "official" by other sources, but their reasoning is pretty convincing (at least as a ballpark):
The year 1948 may be regarded as the annus mirabilis in the emergence of the discipline of signal processing. For in that year Claude Shannon published the epoch-making "A mathematical theory of communication"; Bernard Oliver, John Pierce, and Claude Shannon published the classic argument for the use of pulse-code modulation; modern digital methods of spectrum estimation were introduced; error-correcting codes were introduced; audio engineering achieved a new prominence; and the IEEE Signal Processing Society, albeit under a different name, was established.
That quote is from the beginning of the second chapter, Annus Mirabilis: 1948.
Here's another web page giving some DSP history: http://ethw.org/Oral-History:Alan_Oppenheim
