Many of the films, including work by DW Griffith and starring the original "It Girl", Clara Bow, have not been seen in complete form for more than 70 years. They are to be restored as part of a new project, set up with a US government grant of $1m (pounds 700,000).
At its peak, Hollywood was producing more than 700 silent films a year, but with the advent of "talkies" in 1928, many of them were simply destroyed or left to rot in library vaults.
They were printed on highly-flammable nitrate film stock which has a short shelf life. The film contains animal fats which cause it to decompose.
Archivists at the National Film Preservation Foundation, in San Francisco, have estimated that only 20 per cent of the original silent films have survived and more than half of them need to be restored.
Under the terms of the project, Saving the Silents, film restorers will produce new masters and exhibition prints of 67 shorts, serials and feature films from the first four decades of American cinema, aided by the grant.
The money, which has been given to the Preservation Foundation, which is running the project, will be divided between UCLA's Film and Television Archive, the Museum of Modern Art in New York and George Eastman House, in Rochester, New York State.
Roger Mayer, the chairman of the Preservation Foundation, said: "Time is running out to save the treasures created by America's first film-makers." Kevin Brownlow, a film historian who runs a restoration company, welcomed the US initiative but said more money was needed if the silent movies were not to be lost forever.
"Allowing the silent movies to disintegrate is like throwing away Dickens and Tolstoy because they are old," he said. "I would guess that for the $300m it cost to make Titanic it would be possible to save all the silent films, and it is essential that they are preserved.
"They are part of our history and provide a record of the century. Even if the films are not interesting they show the way of life at the time and what the country looked like."
Mr Brownlow said that in 1929, once the talkies were established many of the silent films were "junked wholesale".
"Sometimes they copied them onto modern stock, but a lot were simply thrown out. Those that were kept were put into vaults where, because they were made on nitrate, they started to decompose."
Restoration involves reprinting the films onto modern stock that has a longer life, but requires careful research to check that scenes which were cut from the original are not being reinstated. It also means hunting for missing reels which have been separated from the main body of the film. One reel of Greta Garbo's 1927 film The Divine Woman turned up in Russia after the war.
Mr Brownlow said every single technical device used in modern cinema was born in the era of the silent movies.
"They could not depend on dialogue so they were forced to develop a visual language and some of the greatest movies ever made were silent," he said.
The films which will be restored include 20 short fiction films by Thomas Edison, one of the inventors of the motion picture camera, War on the Plains (1912), the first Western made by Thomas Ince and a cast of American Indians, and a 1922 version of Sherlock Holmes, starring John Barrymore.
UCLA will also preserve four feature films starring Clara Bow - My Lady's Lips and Poisoned Paradise (1924) and Capital Punishment and My Lady of Whims (1925).
Geoffrey Mcnab, a film writer for The Independent, said silent movies were still relevant today. "Many of them are very accessible and entertaining, and in this digital age it is cultural vandalism to allow them to crumble," he said.
Movie Masterpieces To Be Saved For Posterity
FIVE OF the films that will be preserved by the new initiative...
Manhattan Madness (1916) - This comedy was an early success for Douglas Fairbanks as a cattle salesman returning from Wyoming to his native New York and outwitting his attempted kidnappers. The film was also one of the first directorial successes for Alan Dwan in his 200-film career.
War on the Plains (1912) - First of the 42 silent Westerns directed by Thomas H Ince, who died in 1924. Ince cast American Indians as themselves long before the Western film industry stopped putting shoe polish and feather headwear on their Indians.
Wild and Woolly (1917) - This hour-long comic Western was financed by its star Douglas Fairbanks. He plays Jeff Hillington, a rich city boy sent to Bitter Creek, Arizona, by his railroad magnate father to cure him of his ambition to become a cowboy.
The Roaring Road (1919) - One of the first "road movies", Wallace Reid plays a Grand Prix champion who chases Ann Little's Dorothy Ward, the team boss's daughter, all the way from Los Angeles to San Francisco, not knowing her "kidnapping" is really a ploy to ensure he breaks the 14- hour record for the journey.
Lorna Doone (1922) - The second version of the five screen adaptations of RD Blackmore's novel of the same name. John Bowers plays John Ridd, pursuing a vendetta in 17th century England against the Dunne family. But he has not counted on Dunne daughter Lorna (played by Madge Bellamy) interfering with his quest for justice.