Back in 1984, Seymour B. Cohn and Ralph Levy wrote an article called "A History of Microwave Filter Research, Design, and Development", published in the IEEE Transactions on Microwave Theory and Techniques (Sep 1984). The article covers the foundation of modern filter theory starting from 1937 and proceeding through developments made during and just after World War II. They did a great job, we particularly liked the personal reminiscences from the authors (who were there for a lot of it).
Here's the official abstract:
An account of the development of microwave filters is surveyed, commencing from 1937. Much of the foundation of modem filter theory and practice took place during the period of World War II and the years immediately following, especially by such pioneers as the late P. I. Richards, whose subsequent career is briefly described. Filter topics discussed include low-pass, bandpass, high-pass, and multiplexers constructed in a variety of media such as waveguide, coaxial line, microstrip, and stripline, as well as dielectric resonators. All types of filter characteristics are surveyed, such as Chebyshev, elliptic and pseudo-elliptic function, Achieser-Zolotarev, and a variety of generalized designs, including linear phase.
If you're a member of IEEE, you can download the article from the IEEExplore site (https://ieeexplore.ieee.org/document/1132817) - you just have to log in with your IEEE credentials.
Thanks to Roman for the heads up on this one!