Mannes and Godowsky (two musicians!) invented it back in the 30s, originally as a two-color film (there were quite a few two-color films in the early days, the color rendition was not real good, but it was evidently good enough for some folks) and then when refined to a three-layer film, it went into production. IIRC it started out at ASA 8 (or the equiv in the pre-ASA days). When I started using it in the 1950s, it was ASA 10 (daylight), and Tungsten was ASA 16. There was a "Type F" for a while (for flashbulbs) which I think was ASA 12.
Then in the '60s they came out with "Kodachrome II", which was ASA 25, and sharper than the old ASA 10, with better color rendition. The K25 & K64 replacements came out in the '70s (with the new K14 process), and a lot of folks still lament KII, insisting that the "real reason" for the change was to use less silver.
K200 came out a little later, and there was a "secret" batch (kind of a beta test) of K100 a few years back that a select few got to play with. It never went into production.
The official story on why they killed K25 varies, they can't seem to get their story straight. :) One time they'll say it was because they can't get one of the key ingredients anymore, another time they say it's because the demand has dropped.
I've since heard that it's still in production for 16mm movie film, and if true, that would tend to clobber the first explanation. As to the second reason, when was the last time anyone saw any advertising for any Kodachrome?
My own conjecture is that they're letting it die because 1) E6 films have a better return, 2) they perceive "the market" as favoring speed over quality, and 3) they want to consolidate their lines in order to try to cut their production costs.
I think the "letting it die" theory is supported by the lack of advertising or other promotion.
BTW, E6 -- as well as all other chromogenic films (including C41 and the relatively new black and white C41 films) -- were originally off-limits to Kodak, because Agfa held the patents. After the war ended, the allies divvied up the spoils, negating German patents right and left. That's why there was a proliferation of Japanese cameras based on German designs.
"a lot of folks still lament KII, insisting that the "real reason" for the change was to use less silver."
IMO "the real reason" (in reality, there were likely several) was the changeover to tempered gelatin emulsions, which allowed for higher temp processing, shorter times (faster throughput), and rougher handling. (The tempered color films I've handled wet -- E6 & C41 -- were tougher than "normal" B&W films, whereas the older (i.e., E4) stuff was so delicate that if you looked at it cockeyed the yellow layer would slip off into the wash (literally!). It was almost impossible to hand-process the stuff without at the very least some nontrivial reticulation.)