This list shows a few works of music, literature, and film that, as far as I can tell, were first published in the years shown.  The "Subverted Public Domain" begins with the year 1923.  Works published in that year would already be in the public domain but are still protected by the legislative swindle known as the Sonny Bono Copyright Term Extension Act of 1998. Any United States work published before 1964 lost its copyright in the 28th year after publication unless the copyright was formally renewed at the Copyright Office.   (Congress made renewal automatic for works published after 1963, so most of those works are, and for a very long time will be, under copyright.)  To check on the copyright status of works from the 1923-63 era, it is therefore necessary to determine whether the copyright was renewed.  See How to Determine Whether a Work is in the Public Domain, and links contained there, for more details.

     Frances Hodgson Burnett's The Secret Garden was published in 1911, so it went into the public domain on Jan. 1, 1987.  Its entrance into the public domain has spawned a huge outpouring of new and creative derivative works, including plays, musicals, video and audio cassettes, annotated and searchable online versions, and even cookbooks.  See Derivative Works Based on The Secret Garden.

NOTE:  I have checked the renewals for most of the literary works on this list, so I am confident that they are still under copyright (assuming the CTEA is valid).  Unfortunately, renewals for films and music are not, to my knowledge, as readily available, and I have had to rely heavily on second-hand information.  For example, Lon Chaney's Hunchback of Notre Dame, Buster Keaton's The General, and Douglas Fairbanks, Jr.'s The Thief of Bagdad were on the list, but I have since learned that they appear to be in the public domain and have therefore removed them.  I apologize for any remaining errors.

1919 (entered public domain Jan. 1, 1995)

 Music

  Swanee by George Gershwin and Irving Caesar
  A Pretty Girl Is like a Melody by Irving Berlin

 Books and Poems

   Frances Hodgson BURNETT:  The Secret Garden (1911?)

1920-1921 (entered public domain Jan. 1, 1996 or 1997)

 Music

  AfterYou've Gone  by Henry Creamer and Turner Layton
  Till the Clouds Roll By by Jerome Kern and P.G. Wodehouse
  Over There by George M. Cohan
  Till We Meet Again by Richard Whiting and Raymond Egan
  Ain't We Got Fun
  Ma! (He's Making Eyes At Me)

 Books and Poems

   F. Scott FITZGERALD:  This Side of Paradise
   D.H. LAWRENCE:  Women in Love 
   Edith WHARTON:  The Age of Innocence

Films

  The Kid, with Charlie Chaplin
  The Sheik, with Rudolph Valentino

Characters

  Felix the Cat (appeared in cartoons beginning in 1920; characters go into the PD at the time of the first work in which they appear)
  Hercule Poirot, the Belgian detective, is introduced to readers in "The Mysterious Affair at Styles," by Agatha Christie

1922 (entered public domain Jan. 1, 1998)

 Music

  Look for the Silver Lining by Jerome Kern and Bud DeSylva
  Avalon by Al Jolson, Bud DeSylva, and Vincent Rose

 Books and Poems

T.S. ELIOT:  The Waste Land 
Marcel PROUST:  Swann's Way (first English translation)
James JOYCE:  Ulysses
Oswald SPENGLER:  Decline of the West
Sinclair LEWIS:  Babbitt

 Films

  Blood and Sand with Rudolph Valentino
  Nanook of the North

1923 (should have been public domain Jan. 1, 1999)

 Books and Poems

  Willa Sibert CATHER:  A Lost Lady, Nebraska, and The End Of The First Cycle
  Joseph CONRAD:  Christmas Day at Sea and Outside Literature
  John DOS PASSOS, Streets of Night
  Arthur CONAN DOYLE: The Adventure Of The Creeping Man and The Adventure Of The Sussex Vampire 
  F. Scott FITZGERALD:  Hot and Cold Blood and Invasion of the Sanctuary
  James FRAZER: The Golden Bough
  Robert FROST, New Hampshire (poems0
  Zane GREY:  Code of the West, Steelhead, Tappan's Burro,The Vanishing American, and Down into the Desert
  Ben HECHT:  Fingers at the Window
  Rudyard KIPLING:  Independence and London Stone
  Ring LARDNER:   Blue Beard, Why Authors?, Cinderella, The Dames, What I Ought To Of Learnt In High School, and Bringing Up Children
  Amy LOWELL:  Cut Shadow, Fact, Green Shadows, Rosebud Wall Paper, and Dissonance
  W. Somerset MAUGHAM:  Bewitched, German Harry, Mayhew, and The Force of Circumstances 
  Edna St Vincent MILLAY:  The Harp-Weaver, And Other Poems, Memory of Cape Code, To the Liberty Bell, and The Concert 
  Wallace STEVENS:  Harmonium 
  Booth TARKINGTON:  The Coincidence, The Power of the Press, and The Midlander 
  P.G. WODEHOUSE: Jeeves, First Aid for Dora Heart of a Goof, Leave It to Psmith, Magic Plus Fours, No Wedding Bells for Him,The Return Of Battling Billson, Rollo Podmarsh Comes To, Ukridge Rounds A Nasty Corner, and Chester Forgets Himself 
  Virginia WOOLF:  Jacob's Room
  William Butler YEATS:  Meditations In Time Of Civil War

 Plays

  Noel COWARD:  The Young Idea 
  Luigi PIRANDELLO (trans Arthur Livingston):  Each In His Own Way, And Two Other Plays

 Films

Safety Last by Harold Lloyd
Little Church Around the Corner
The Ten Commandments, by C.B. DeMille

Music

You're The Cream In My Coffee, words and music by B.G. De Sylva, Lew Brown and Ray Henderson
Who's Sorry Now?, words and music by Bert Kalmar, Ted Snyder, And Harry Ruby
I Cried For You (Now It's Your Turn To Cry Over Me), by Arthur Freed, Gus Arnheim and Abe Lyman
Chansonette, music by Rudolf Friml, lyrics by Irving Caesar, Dailey Paskman, and Sigmund Spaeth
Yes! We Have No Bananas, by Frank Silver and Irving Cohn
Charleston, by Mack & Johnson

1924 (should have been public domain Jan. 1, 2000)

 Films

  The Battling Fool (Columbia), with William Fairbanks, Pat Harmon, Eva Novak, and Edward Kennedy; written and directed by W.S. Van Dyke 
  Dixie
  The Fighting Coward (Famous Players - Lasky), with Cullen Landis, Ernest Torrence, Mary Astor, and Noah Beery; produced and directed by James Cruze
  He Who Gets Slapped (MGM), with Lon Chaney, Norma Shearer, and John Gilbert; directed by Victor Seastrom (Sjöström)
  Monsieur Beaucaire (Famous Players - Lasky), with  Rudolph Valentino, and Bebe Daniels; produced and directed by Sidney Olcott
  The Next Corner (Paramount), with Conway Tearle, Lon Chaney, and Dorothy Mackaill; directed by Sam Wood (still under copyright because of the CTEA, but considered lost)
  Peter Pan (Paramount), with Betty Bronson, Ernest Torrance, and Mary Brian; produced and directed by Herbert Brenton
  Racing for Life (Columbia), with William Fairbanks, Eva Novak and Edgar Kennedy
  Sherlock, Jr.
  

Books

  
  Mark Twain, Autobiography (posthumous)
  Edna Ferber, So Big

Music

When My Sugar Walks Down The Street (All The Little Birdies Go Tweet Tweet Tweet), words and music by Gene Austin, Jimmy McHugh and Irving Mills
It Had To Be You, lyric by Gus Kahn, music by Isham Jones
Rhapsody in Blue, by George Gershwin (performed, by the composer, for the first time Feb. 12, 1924, accompanied by Paul Whiteman's orchestra)
Fascinating Rhythm; The Man I Love, by George & Ira Gershwin
Sleepy Time Gal, lyric by Jos. R. Alden and Raymond B. Egan
Amapola
Everybody Loves My Baby, words and music by Jack Palmer and Spencer Willson
All Alone; They Call It Dancing; Lazy; What'll I Do?, words and music by Irving Berlin
I'll See You In My Dreams, lyrics by Gus Kahn, music by Isham Jones
Moonlight And Roses, by Edwin H. Lemare, Ben Black and Neil Moret
Memory Lane, lyrics by B.G. De Sylva, music by Larry Spier and Con Conrad
When Day Is Done, lyrics by B.G. De Sylva, music by Dr. Robert Katscher
Rose Marie; Indian Love Call; Totem Tom Tom, from the musical play and film Rose Marie, music by Rudolph Friml and Herbert Stothart, book and lyrics by Otto Harbach and Oscar Hammerstein 2nd
Golden Days; Just We Too; Deep In My Heart, Dear (Sorry, Dad), from The Student Prince, by Sigmund Romberg
California, Here I Come, by Jolson, De Sylva & Meyer
Tea for Two, by Caesar & Yeomans

Characters

Little Orphan Annie, drawn by Harold Gray, debuts in the New York Daily News Oct. 5, 1924

1925 (should have been public domain Jan. 1, 2001)

 Films

  The Gold Rush, with Charlie Chaplin.  Copyright was never renewed in this work, so it went into the PD in 1953.  Apparently Chaplin composed a musical score and added it to the film, registering a copyright in 1942 as a derivative work (which copyright was renewed in 1969).  That copyright, however, covers only the new material added to the original, not the original or any elements of the original themselves.  It seems that someone has nevertheless filed a restoration notice to revive the original silent film copyright under the Uruguay Round Agreements Act.  (The constitutionality of that is under challenged in Golan v. Ashcroft - see Challenge to Constitutionality.)  But if the original silent film was a U.S. work, a restoration notice could not validly be filed as to it.  That, in turn, depends on where the work was first "published."  If it was published first in the U.S., The Gold Rush should be in the public domain.  (I am indebted to Michael Agee for apprising me of these twists and turns in the saga of The Gold Rush.)
  Battleship Potemkin (possibly PD in any event, because of status of US/Soviet copyright relations) 
  His People, also known as Proud Heart (Universal),   with Rudolph Schildkraut, George Lewis, Jean Johnson, Kate Price, and Edgar Kennedy; directed by Edward Sloman

Books

Robert BENCHLEY, Pluck And Luck
Stephen Vincent Benet, Tiger Joy, A Book Of Poems
Willa CATHER, The Professor's House
George M. COHAN, Mud Pies And Maple Sugar and Poor Little Rich Man
John DOS PASSOS, Manhattan Transfer
Theodore Dreiser, An American Tragedy
Andre (Paul Guillaume) GIDE, Les Faux-Monnayeurs
Samuel GOMPERS, Seventy Years Of Lide And Labor
Zane GREY, Tales Of Fishing Virgin Seas and The Thundering Herd
Ernest HEMINGWAY, In Our Time
Aldous HUXLEY, Along the Road
Franz KAFKA, Der Prozess (The Trial)
John Maynard KEYNES, The Economic Consequences Of Sterling Parity, aka: The Economic Consequences Of Mr Churchill
Rudyard KIPLING, Warfare On Ill Will, Chartres Windows, A Choice Of Songs, and The Shipping Industry
Ring LARDNER, You Know Me Al and What Of It 
Sinclair LEWIS, Arrowsmith
Walter LIPPMANN, The Phantom Public
Archibald Macleish, The Pot of Earth
W Somerset MAUGHAM, The Painted Veil
Luigi Pirandello, Dal Naso Al Cielo, Quaderni Di Serafino Gubbio, Operatore,  and Donna Mimma
Edwin Arlington ROBINSON, Dionysus In Doubt
Bertrand RUSSELL, What I Believe and The ABC Of Relativity
Booth TARKINGTON, Mrs Leslie Braithwaite's Husband, Rabble Rouser, and Napoleon Was A Little Man
Albert Payson TERHUNE, Wolf and Najib
Lowell THOMAS, Beyond Khyber Pass and The First World Flight
H.G. WELLS, A Year Of Prophesying
Edith WHARTON, The Writing Of Fiction
P.G. WODEHOUSE, In The Springtime
Virginia WOOLF, The Common Reader and Mrs Dalloway
William Butler YEATS, Early Poems And Stories

Music

I'm Tired of Everything But You, words and music by Isham Jones
Manhattan, lyrics by Lorenz Hart, music by Richard Rodgers
Angry, lyrics and arrangement by Dudley Mecum, Henry and Merritt Brunies, and Jules Cassard
Remember; Always; Florida By The Sea; Paddlin' Madelin' Home, words and music by Irving Berlin
Dinah, words by Sam M. Lewis & Joe Young, music by Harry Akst
Side By Side, words and music by Harry Woods
Cecilia (Does Your Mother Know You're Out?), words by Herman Ruby, music by Dave Dreyer
Jalousie, music by Jacob Gade, words by Vera Bloom
Five Foot Two, Eyes Of Blue, lyrics by Sam M. Lewis and Joe Young, music by Ray Henderson
Valencia (A Song Of Spain), words by Lucien Boyer and Jacques-Charles, music by Jose Padilla, American version by Clifford Grey

1926 (should have been public domain Jan. 1, 2002)

  Music

  Irving Berlin:  Blue Skies
  Rodgers & Hart:   The Blue Room, from The Girl Friend 
  Sigmund Romberg:  The Desert Song and The Student Prince 
  Harry Woods:  When the Red, Red Robin Comes Bob, Bob Bobbin' Along

Films

The Lodger (Alfred Hitchcock)
The Vanishing Americans (Paramount)

Books

Ernest HEMINGWAY, The Sun Also Rises
A.A. MILNE, Winnie the Pooh
Watty PIPER (Mabel C. Bragg), The Little Engine That Could

 1927 (should have been public domain Jan. 1, 2003)

 Music

Oscar Hammerstein II and Jerome Kern:  Ol' Man River and Showboat

Films

Wings
The Jazz Singer, with Al Jolson
Sunrise
Metropolis

1928 (should have been public domain Jan. 1, 2004)

 Characters

Mickey Mouse