Film not preserved properly can be lost forever. The preservation list has grown to 300 in the past 12 years.
The librarian of Congress named 25 classic films for preservation in the National Film Registry, from Bela Lugosi's Dracula, a grandparent of today's horror movie, to the cinematic record of President William McKinley's inauguration in 1901.
"Fifty percent of the films produced before 1950 and at least 90 percent made before 1920 have disappeared forever," librarian James Billington said in announcing the list this week. "And, ominously, more films are lost each year."
The additions bring to 300 the number of films selected for the preservation registry in the past 12 years, chosen for both their historical and entertainment values.
The library contains the world's largest collection of film _ more than 300,000 film and television titles. It arranges preservation of those in the registry through its own program in Dayton, Ohio, and by collaboration with other institutions.
Nitrates deteriorate in older film, and colors fade. In the late 1980s, it was found that even acetate-based "safety film" is subject to what technicians call the "vinegar syndrome."
Steve Leggett, staff coordinator of the National Film Preservation Board, said film has to be kept at temperatures near freezing and as dry as possible to prevent the acetate base from dissolving into acetic acid, the main acid of vinegar. Film not preserved under the best conditions becomes impossible to run through projectors, Leggett said.
This year's registry list begins with Francis Ford Coppola's Apocalypse Now, starring Marlon Brando _ a 1979 updating of Joseph Conrad's classic novel Heart of Darkness, with the story set in Vietnam instead of Africa. It ends with Will Success Spoil Rock Hunter? starring Tony Randall, Jayne Mansfield and Groucho Marx, a spoof of the advertising industry from 1957.
In between come a range of films, from fantasies like the Peter Pan of 1924 to Frank Capra's seven-film World War II series, Why We Fight, produced by the U.S. Army between 1943 and 1945.