The 1964 Broadway musical Hello, Dolly! was based on Thornton Wilder's 1955 play The Matchmaker, which, in turn, had been based on earlier sources. It told the story of a turn-of-the-century widow matchmaker in New York who ends up matching herself to one of her clients. The score was written by 30-year-old Jerry Herman; it was his second Broadway show, following 1960's successful Milk and Honey. The setting allowed the composer to write songs with the flavor of 1900s Tin Pan Alley and a Dixieland feel. Among these was the title tune, which came at that point in the second act of the show when the main character, Dolly Levi, originally played by Carol Channing, returns to the Harmonia Gardens, an expensive New York restaurant she has not been to since the death of her husband. She greets the waiters warmly (among them, one named Louie), then they reply as a chorus.
At the end of 1963, 62-year-old Louis Armstrong remained the jazz legend he had been for most of his life, but he had been out of the limelight for some time. Jazz had veered away from popular music in the late '40s, and it had veered away from Armstrong's style of playing in the '50s. He continued to tour regularly and to record occasionally, but he appeared to be in the twilight of his career. In December 1963, at the behest of his manager, Armstrong made a demonstration recording of "Hello, Dolly!" for the song's publisher to use to promote the show. Hello, Dolly! opened on January 16, 1964, and became a major success. The same month, Kapp Records released Armstrong's publishing demo as a commercial single. With its banjo introduction and Armstrong's inimitable interpretation ("This is Louis, Dolly," he sang, using, as he always did, the formal version of his first name), and backed by the success of the show (which, of course, it also promoted), the record became a hit; by May, it was number one. Meanwhile, an original Broadway cast album of Hello, Dolly! had been recorded and released, of course, with Carol Channing and the cast singing the title song, and that album hit number one in June. Even more successful, however, was Armstrong's own Hello, Dolly! LP, as Kapp Records hastily put him in the studio to record a bunch of songs to fill up a 12" album and it, too, topped the charts. As a result of all this attention, "Hello, Dolly!" won the 1964 Grammy Award for Song of the Year.
The success of "Hello, Dolly!" had an unintended consequence. Songwriter Mack David heard a similarity to the melody of his own composition, "Sunflower," which had been a chart hit for six different artists 15 years earlier, most successfully Russ Morgan, and become the state song of Kansas -- the tunes are not exactly the same, but you can certainly sing "You're my sunflower" to the refrain of "Well, hello, Dolly." David sued for plagiarism and ended up a quarter of a million dollars richer. But Herman still made out well: Hello, Dolly! became the longest running Broadway musical in history up to its time, with a run of 2,844 performances. Carol Channing was succeeded by Ginger Rogers, Martha Raye, and Betty Grable, while Mary Martin starred in the London production (and was featured on the London cast album). Then, on November 12, 1967, an all-black cast began performing Hello, Dolly! on Broadway with Pearl Bailey in the title role and Cab Calloway as her co-star. A second cast album featuring this cast was recorded. (Eventually, even Ethel Merman turned up on Broadway in the role.) In 1969, a movie version of Hello, Dolly! was released with Barbra Streisand starring. Louis Armstrong guest starred in the film, dueting with Streisand on what had become a late-career signature song for him. Both Channing and Bailey starred in Broadway revivals in the '70s, and Channing appeared in yet another Broadway revival in the 1990s.
"Hello, Dolly!" was one of the last major pop hits to come from Broadway at a time when Broadway music and pop music were diverging. Of course, it succeeded as a novelty because it was really a throwback, a pastiche of early 20th century styles. Nevertheless, it became a standard, recorded by dozens of middle-of-the-road performers who, by the mid-'60s, were desperate for new material; it served them well, and it continues to be a well-known and popular song.