While it's true Capra may not have made many technical innovations in cinema, I still think that many of his films were ahead of their time in depth and story, a prime example being "It Happened One Night." When you compare it romantic comedies made up until that point, I think it's a large step forward and continues to influence that genre even today.
"I know you're in there, Fagerstrom!"-Conan O'Brien

DonRogers-Your outline is quite good. Thanks for posting that.
If I were asked to compile a list of "Hollywood landmarks", I'd probably be a little less "specific"; that is, I probably wouldn't include Disney alone, for instance, or individual genres, as landmarks, but rather look at influential works that spread across entire genres and impacted many filmmakers.
I'd also probably limit myself to the 1950s, when motion pictures ceased to be the predominant art form that it had been from roughly the 1910s to the postwar period.
That said, here's my outline:
"The Birth of a Nation"-This film both established Griffith as a major artist, the first director perhaps to really be recognized as such, and gave the motion picture a respectability that it had previously lacked, establishing the feature film once and for all as a viable form. Most important to this discussion is the fact that the film really established Hollywood as the center of film production in America, due largely to the variety of locations, the rural areas which were ideal for building large-scale sets for historical films as well as providing "natural" locations, and the growing number of independent producers who worked outside of the established Patents Trust in the East.
"Greed"-If "The Birth of a Nation" represented the great rise and success of independent producers, "Greed" represents the reversal of that power back to established studios. This, of course, began in the early 20s and was largely the idea of boy wonder producer Irving Thalberg, who believed the studio, and by proxy, the producer, should hold total and complete control in all decisions related to filmmaking. The butchering of "Greed" in 1924 can be seen as the birth of the studio system, which would really take place with the coming of sound, when increased necessity for technical resources and larger technical crews working in studio sound stages drove the last of the independents out of business.
"The Jazz Singer"-listed here as the film that really proved what could be done with sound technology, and ushered in the era of star- and producer-driven films.
"The Public Enemy"-Instrumental in bringing Broadway theatrical performance traditions to film acting, ushering in the generation of theatre-trained actors such as Cagney, Tracy and Stewart.
"42nd Street"-Musical films in particular represented large technical leaps in moving the camera again, synchronizing pre-recorded music playback with the picture, and generally making the talking film more "cinematic".
"Gone with the Wind"-represents a major film made by an independent producer (Selznick) which was the first epic of this scale made in the talking picture medium. It would set the standard for the post-war epic, and can be seen as the height of studio-era glamor, star-power, and the "auteurist" voice of the producer.
"Citizen Kane"-along with works by Sturges, Huston, Wyler and others, this film by Orson Welles represents the turning of the power back to the director.
"Double Indemnity"-significant as an example of the existentialism that began appearing in American film during and after WWII. This marks a significant change from the kind of straightforward "sunny optimism" and populist themes of the Depression era.
"The Best Years of Our Lives"-classic example of postwar Hollywood cinema, moving toward "Big Important Subjects" and an increased influence from Italian Neorealism. Also significant as an example of the increasing treatment of individual films as "events", as a result of the Paramount Decision which ended the studios' monopoly hold on theatrical venues.
"Ben-Hur"-the testament to an end of an era. Hollywood's Golden Age ended with the decade that saw an incredible rise in popularity in other media-specifically television, and the rock and roll/pop music industry. The studios themselves had already turned into more or less distribution arms for films produced independently, or at least took a kind of "collaborative" role in the production of films-providib68ng production facilities, crew, and a percentage of the budget.

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Excellent post donrogers.

Thanks,
donrogers42
! Much appreciated!

Here are some significant films in (American) film history, arranged more or less chronologically. Sorry not many Capra films here (also among my favorites, no Buster Keaton, Ernst Lubitsch, Alfred Hitchcock, Preston Sturges, Orson Welles, George Cukor, or Elia Kazan; and not enough John Ford or Stanley Kubrick).
The early years:
The Great Train Robbery
D.W. Griffith and the first American film epics:
The Birth of a Nation/Intolerance
Chaplin and silent comedy:
The Kid/Modern Times
The studio system:
Greed/A Star is Born (1937)
The sound era begins:
The Jazz Singer/Top16d0 Hat/42nd Street/Singin' in the Rain
The rise of Disney:
Steamboat Willie/Snow White and the Seven Dwarfs
The fast-talking 30s:
Scarface (1932)/It Happened One Night/My Man Godfrey/His Girl Friday
1939 "Hollywood's greatest year":
Gone With the Wind/The Wizard of Oz
Hollywood goes to war, and comes home:
Casablanca/They Were Expendable/The Best Years of Our Lives
"Film noir":
The Maltese Falcon/Double Indemnity/The Big Sleep/Sunset Blvd.
Responding to television the widescreen epic:
The Bridge on the River Kwai/Spartacus/Lawrence of Arabia
The rise of the "star system" and the decline of the studios:
Winchester 73/Cleopatra
Changing standards and the onset of the "culture wars":
The Moon is Blue/Who's Afraid of Virginia Woolf?/Easy Rider/The Graduate/The Wild Bunch/Midnight Cowboy/Deep Throat
The "disaster film":
Airport/The Poseidon Adventure/The Towering Inferno/Airplane!
The director's era (1971-1975):
The Godfather, Part 2/Mean Streets/The Last Picture Show
The rise of the blockbuster:
The Exorcist/Jaws/Star Wars

This is a huge question!!! It would be too big if we had to chose only silent films.
I'm not so sure Capra made many technical discoveries. His contribution was more in the genre filed and by creating the "American National Religion." Capra was one of the main contributors to the American Identity. He formed in to words and pictures what America stood for, or at least what it should stand for. So if I would chose from his films then I would chose It Happened One Night because almost all romantic comedies have followed it. Mr. Smith Goes to Washington because it shows the "American National Religion" so well.

This comment is most likely authentic and fairly close to what I intended to say