Intended as an antidote for the increasingly racially and politically charged climate of everyday life in the United States, the song also has a hopeful, optimistic tone with regard to the future, with reference to babies being born into the world and having much to look forward to. The song was initially offered to Tony Bennett, who turned it down. Thereafter, it was offered to Louis Armstrong. George Weiss recounts in the book Off the Record: Songwriters on Songwriting by Graham Nash that he wrote the song specifically for Louis Armstrong. Weiss was inspired by Armstrong's ability to bring people of different races together. The song was not initially a hit in the United States, where it sold fewer than 1,000 copies because ABC Records head Larry Newton did not like the song and therefore did not promote it, but was a major success in the United Kingdom, reaching number one on the UK Singles Chart. In the US, the song hit #116 on the BillboardBubbling Under Chart. It was also the biggest-selling single of 1968 in the UK where it was among the last pop singles issued by HMV Records before becoming an exclusive classical music label. The song made Louis Armstrong the oldest male to top the UK Singles Chart, at sixty-six years and ten months old. Armstrong's record was broken in 2009 when a cover version of "Islands in the Stream" recorded for Comic Relief—which included the 68-year-old Tom Jones—reached number one in that chart. Tony Bennett did go on to cover "What A Wonderful World" several times, as in 2003 with K.D. Lang, paying homage to Bennett's friend Armstrong.
ABC Records' European distributor EMI forced ABC to issue a What A Wonderful World album in 1968 (catalogue number ABCS-650). It did not chart in the US, due to ABC's not promoting it, but charted in the UK where it was issued by Stateside Records with catalogue number SSL 10247 and peaked on the British chart at No. 37.
The song gradually became something of a standard and reached a new level of popularity. In 1978, Armstrong's 1967 recording was featured in the closing scenes of the first series of BBC radio's cult hit, The Hitchhiker's Guide to the Galaxy, and was repeated for BBC's 1981 TV series of the same. In 1988, Armstrong's recording was featured in the film Good Morning, Vietnam, in which a DJ played it on the radio in 1965—two years before it was recorded—and was re-released as a single, hitting #32 on the US Billboard Hot 100 chart in February 1988. The single charted at number one for the fortnight ending June 27, 1988 on the Australian chart.
The song was also used in the first five episodes of the ABC sitcom Family Matters, before being replaced by an original theme song, "As Days Go By", sung by Jesse Frederick.
In 2001, rappers Ghostface Killah, Raekwon and The Alchemist released "The Forest," a song that begins with three lines of lyric adapted from "What a Wonderful World", altered to become "an invitation to get high" on marijuana. The rappers and their record company, Sony Music Entertainment, were sued by the owners of "What a Wonderful World," Abilene Music. The suit was thrown out of court after Judge Gerard E. Lynch determined that the altered lyric was indisputably a parody, transforming the uplifting original message to a new one with a darker nature.
As of April 2014, Louis Armstrong's 1967 recording has sold 2,173,000 downloads in the US after it was released digitally.
1999: Anne Murray, on her platinum release of the same name, which also spawned a book and video. The album reached number one on the US Contemporary Christian charts, number 4 on the US Country charts, and number 38 on the top 200.