WASHINGTON (AP) _ President Reagan, saluting the 50th anniversary of animated feature films, hailed ''Snow White and the Seven Dwarfs'' on Saturday as a milestone in America's artistic history.

Reagan, in a proclamation released by the White House, said the nation should be grateful for an art form ''that brings to the screen such magic and lasting vitality.''

The president, a former actor, also praised such animated films as embodying ''fundamental values of good over evil, courage, and decency that so many Americans cherish.''

''Fifty years ago, a milestone in our nation's artistic history was achieved when 'Snow White and the Seven Dwarfs' became the first full-length animated feature film,'' the proclamation said.

''The achievements of the motion picture art that have followed since the debut of the first feature-length animated film in 1937 have mirrored the artistic development of American culture ...,'' Reagan said.

The film, which has been made available again, was first released on Dec. 21, 1937, by cartoonist Walt Disney.