Since its release in 1939, “The Wizard of Oz” has touched generations of Americans: The movie is family viewing tradition for millions, and its iconic songs — from “Over the Rainbow” to “We’re Off to See the Wizard” — have been part of the nation’s playlist for decades.

Those songs and others from the film were written by two of the most accomplished songwriters working in Hollywood and on Broadway: lyricist Yip Harburg and composer Harold Arlen. Harburg had penned the lyrics for classics such as “April in Paris” and “Buddy, Can You Spare a Dime?” Arlen would compose over 500 songs, many of them standards: “Come Rain or Come Shine,” “Stormy Weather,” “Ac-Cent-Tchu-Ate the Positive,” “The Man That Got Away.”

With “Oz,” Arlen and Harburg reached the pinnacle of their public recognition — and especially with “Over the Rainbow,” which won the Oscar for best original song and today is regarded as one of the 20th century’s greatest songs.

In 2022, the Library began acquiring important manuscript and archival materials related to Arlen’s work. The Harold Arlen Collection, which came to the Library from his sister-in-law, Rita Arlen, includes musical sketches, correspondence from notable show business colleagues and friends, photographs, scripts and even works of art, including a George Gershwin self-portrait.

Most recently, the Library acquired a blockbuster collection of original music and lyric manuscripts and sketches for the “Oz” film.

A star of the collection: The only lyric sketch for “Over the Rainbow” known to exist. “Some day I’ll wish upon a star + wake + find the darkness far behind me,” Harburg scrawled in pencil on a scrap of yellow legal paper. Eighty-five years later, Harburg’s phrases still hold their emotional power: There is magic in seeing those lines and thinking of Judy Garland singing them, accompanied by chirping birds and lush orchestration.

Researchers long have been curious about how the film’s songs were written; the Arlen Collection can answer many of their questions.

Among the highlights are over 30 pages of music sketches that hint at how Arlen conceived motifs for the soundtrack, connecting each song musically. The composer’s music manuscripts reveal both his first thoughts for the film’s score as well as fully developed sections that became the score we know. Manuscripts are replete with his brief musical thoughts, rapidly yet confidently jotted down. Numerous sketches appear to be random, and many ideas clearly were abandoned quickly.

Still, amid a page of unfamiliar melodic snippets, an instantly recognizable tune suddenly will appear. In one instance, it’s the tune for the opening of “Ding-Dong! The Witch is Dead,” with a dummy lyric.

The newly acquired materials contain another gem related to “Over the Rainbow”: a short music sketch that may be a precursor to the song. A series of notes feature the famous octave interval sung on the first instance of the word “Somewhere,” with a rhythm and note sequence very similar to the final version (though scholars who have viewed the document are divided about the connection).

The unidentified sketch might never be definitively connected to the famous song, but the chance for future discovery in these sketches is thrilling.