The history of horror

When doing my research i decided to do some research into the history of the genre of horror. I got my information from 

http://horror.about.com/od/horrorthemelists/ss/horrortimeline.htm

It didn't take long after the advent of motion picture technology in the late 19th century for filmmakers to dabble in the horror genre, as witnessed by French director Georges Méliès' 1896 short The House of the Devil, often credited as being the first horror movie. Although America was home to the first Frankenstein and Jekyll and Hyde movie adaptations, the most influential horror films through the 1920s came from Germany's Expressionist movement, with films like The Cabinet of Dr.Caligari and Nosferatu influencing the next generation of American cinema. Actor Lon Chaney, meanwhile, almost singlehandedly kept American horror afloat, with The Hunchback of Notre Dame, The Phantom of the Opera andThe Monster, which set the stage for the Universal dominance of the '30s.

Looking back as far as the late 18th century these following films are considered the first films that sparked the horror phenomenon off.

1896: The House of the Devil, 1910: Frankenstein, 1913: The Student of Prague, 1920: Cabinet of Dr. Caligari, 1920: The Golem: Or How He Came into the World, 1920: Dr. Jekyll and Mr. Hyde, 1922: Haxan. 

These are just a few films that are considered most famous and The house of the Devil is said to be the first ever horror film. 

Moving onto the mid 19th century a lot changed within the horror world and various cultural forces helped shape horror movies in the '50s. The Cold War fed fears of invasion (Invasion of the Body Snatchers, The Thing from Another World, The Blob), nuclear proliferation fed visions of rampaging mutants (Them!,The Beast from 20,000 Fathoms, Godzilla) and scientific breakthroughs led to mad scientist plots (The Fly). 

Moving onto the 60s a lot changed because of social rebellion and the decade that saw hippies and peace breaking new grounds throughout the world so people decided to get more experimental in the film industry. Perhaps no decade had acclaimed horror films than the '60s. Reflecting the social revolution of the era, the movies were more edgy, featuring controversial levels of violence (Blood Feast, Witchfinder General) and sexuality (Repulsion). Films like Peeping Tom and Psycho were precursors to the slasher movies of the coming decades, while George Romero's Night of the Living Dead changed the face of zombie movies forever. 

During the 70s exploitation movies hit their stride in the decade, boldly flouting moral conventions with graphic sex (I Spit on Your Grave,Vampyros Lesbos) and violence (The Texas Chainsaw Massacre, The Hills Have Eyes)

The 80s saw comedic and horror being mixed together to create films such as Evil Dead 2 and House. 

The early '90s brought unrivaled critical acclaim for the horror genre, with The Silence of the Lambs sweeping the major Academy awards in 1992, a year after Kathy Bates won the Oscar for Best Lead Actress for Misery and Whoopi Goldberg won for Best Supporting Actress for Ghost. Such success seemed to spur studios into funding large-scale horror-themed projects, such as Interview with the Vampire, Bram Stoker's Dracula and Wolf. In 1996, Scream's runaway success reignited the slasher flame, spawning similar films, such as I Know What You Did Last Summer and Urban Legend. At the end of the decade, Blade foreshadowed the coming flood of comic book adaptations, and Asian horror movies like Ringuand Audition signaled a new influence on American fright flicks. Meanwhile, 1999 witnessed two of the biggest surprise hits of the decade, regardless of genre, in The Sixth Sense and The Blair Witch Project.

Twenty-first century horror in the US has been identified with remakes of both American (Friday the 13th, Halloween, Dawn of the Dead) and foreign films (The Ring, The Grudge), but there have been innovations within American horror -- most notably the "torture porn" of Saw and Hostel fame.
Altogether by doing this research i have found that horror films have got more and more graphic and gory so most are considered rated 18 these days because film producers feel the need to push the envelope as everything has been done before. This then fuelling the popularity of remakes in the 20th century.