Film Noir

*Film Noir, (French for "black film"),  was coined by French film critics who noticed the trend of how 'dark', the looks and themes were of many American crime and detective films of the time.

Mostly shot in gloomy grays, blacks and whites, and showed the dark and inhumane side of human nature with cynicism and doomed love, and they emphasized the brutal, unhealthy, seamy, shadowy, dark and sadistic sides of the human experience.  *Filmsite.org 

One of my favorite quotes explaining whether you are watching film noir or not, is written by Eddie Muller:

"If a private eye is hired by an old geezer to prove his wife's cheating on him and the shamus discovers long-buried family secrets and solves a couple of murders before returning to his lonely office – that's detective fiction. If the same private eye gets seduced by the geezer's wife, kills the old coot for her, gets double-crossed by his lover and ends up shot to death by his old partner from the police force – I can say with complete assurance: you are wallowing in NOIR.

The film noir period of filmmaking lasted from about 1940-1958.

I'll defer to most experts (film critics, film historians, and film buffs) who say that "Stranger On The Third Floor", released in theatres on August 16, 1940, was the first true film noir ever made. The same experts generally agree that the last of the true noir films was Orson Welles' "Touch Of Evil" released in 1958.

Film noir probably reached it's peak in the late 1940s, although there were very good films made in the 1950s. 

Still not sure what makes a movie.. Film Noir? 

Even the theme music from the movies are worth a listen.