
What was Kodachrome? Why was it so loved? When production and processing ceased in 2010 it was a front page story.
When Kodachrome was released on the market in 1935 it became the first colour film to succeed in the mass market, establishing colour photography as a viable option for amateurs and professionals alike. Before Kodachrome, making photographs in colour was an arcane science mastered by only a few. The Colour-Carbro process required colour separations to be made first and then printed sequentially in perfect registration on the receiving paper. It was hard, slow and very expensive.
When Kodachrome arrived in 1936 it brought simplicity to colour photography: you shot the film and Kodak processed it, and that was it. A box of colour slides was posted to you a week later and the colours were realistic and beautiful. 
The actual invention of Kodachrome is a story in itself. The inventors were two young American musicians, Leopold Godowsky Jr. and Leopold Mannes. They became known as God and Man. Both were high achievers. Godowsky studied music at UCLA and became a violinist with the San Francisco Symphony. Mannes studied piano at Harvard and earned a Pulitzer Scholarship and a Guggenheim fellowship, playing professional piano – all this while studying physics at Harvard. They came from high achieving families. Godowsky’s father was the most famous concert pianist of his day and Mannes also came from a renowned classical music family.
All this makes it so odd that in their spare time they were inventing colour film. In 1917 they had seen a crude colour film at a cinema and thought they could do better. They tinkered for years with their process until family connections help them get financing for their research. Eventually Kodak noticed and invited them to work at Rochester, Kodak’s HQ. 
In 1935, Kodak released its 16mm cine Kodachrome and a year later 8mm cine and 35mm still films, all very successful and the beginning of a 75 year story. How did it work? Well, wikipedia explains it thus:
Kodachrome film was coated with three layers of ordinary black-and-white silver halide gelatin emulsion, but each layer was made sensitive to only one-third of the spectrum of colors—in essence, to red, green or blue. Special processing chemistry and procedures caused complimentary-colored cyan, magenta or yellow dye images to be generated in these layers as the black-and-white silver images were developed. After they had served their purpose, the silver images were chemically removed, so that the completed chromogenic film consisted solely of the three layers of dye images suspended in gelatin.
Kodachrome gave spectacular colour and great longevity. I have slides a half century old and there’s no fading, while other brands have decayed badly. The crisp, vivid palette was very appealing and the slides were also very sharp. Kodachrome was available in 25 ISO which became the preferred choice for landscape and geographic photographers for its fine detail – enlargements from 35mm were no problem. Other speeds and size formats were also available for different purpose, including 5×4 and 10×8 – imagine!
4×5 Kodachrome transparency by Alfred Palmer. October 1942. “Noontime rest for an assembly worker at the Long Beach, Calif., plant of Douglas Aircraft Company. Nacelle parts for a heavy bomber form the background.”
One eccentricity of the film was its weird processing. Because of the special emulsion only a handful of labs worldwide could accomplish the difficult process. In the 1940s, Kodak brought the Ektachrome range of transparency films which had a much simpler developing process. This continues, although it’s running out of steam in the face of digital photography’s superior colour control.
What happened to God and Man? After inventing Kodachrome, Mannes returned to music, becoming a concert pianist and composer. Godowsky pursued a career as a concert violinist with the Los Angeles and San Francisco Symphonies while also becoming a painter and sculptor. Somehow he found the time to get married – to George Gershwin’s sister! I told you they were high achievers.
Kodachrome
They give us those nice bright colors
They give us the greens of summers
Makes you think all the world’s
A sunny day, oh yeah
I got a Nikon camera
I love to photograph
So mama, don’t take my Kodachrome away Paul Simon