->''"Radio plays 'em, record stores sell 'em, ''Magazine/{{Billboard}}'' ranks 'em, and ''[=AT40=]'' counts 'em down.''"
-->-'''Creator/CaseyKasem'''

''American Top 40'' is a weekly, [[LongRunner long-running]] (1970-present, with a three-year hiatus in TheNineties) syndicated radio program, originally hosted by CaseyKasem and currently hosted by RyanSeacrest, which counts down the [[ExactlyWhatItSaysOnTheTin forty most popular]] radio songs in the United States.

In addition to playing the week's most popular songs, ''[=AT40=]'' frequently included various extra segments. Perhaps most famous among these was Kasem's "Long Distance Dedication": a write-in request from a listener for a particular song, always sentimental in nature, typically directed at a person the listener had not seen in a considerable amount of time (such as a long-distance romantic couple, wife to overseas-based military husband, someone's birth parent on the other side of the country, etc). These particular segments were best remembered for the emotional tone with which Kasem would read the requests on air.

In 1988, Kasem left the show and was replaced by ShadoeStevens. The change, as well as an altered format, went over poorly, and ''[=AT40=]'' was eventually cancelled in 1995. Kasem, though, had in the meantime started up a [[DuelingShows rival program]], ''Casey's Top 40'', and eventually managed to acquire the rights to the ''American Top 40'' title, and the show was UnCancelled in 1998. Kasem subsequently retired from the program in 2004; Ryan Seacrest took over hosting duties and helms ''[=AT40=]'' to this day, though on an especially busy week for [[JackOfAllTrades the host/producer/cable network owner/''Today Show'' contributor]], a guest host (usually a top-charting artist) will do the show for Seacrest instead.

Song-ranking data was originally derived from ''Magazine/{{Billboard}}'' Magazine's "Hot 100" pop/rock singles chart before switching over to ''Radio and Records'' (which Kasem had used in his competing program) in 1998. Currently, songs are ranked by data from Mediabase, combined with results of [[AudienceParticipation listeners voting for their favorite songs online]].

In the mid-1980s, ''American Top 40'' also had a MusicVideo equivalent: ''America's Top 10'', which was basically the last hour of the radio program -- that is, the ten most popular songs on the ''Billboard'' chart -- translated to television, using clips from the songs' videos, natch. Other similar programs have included:
* ''Weekly Top 40'', hosted by radio personality Music/RickDees;
* ''Casey's Top 40'', hosted by Kasem himself when he left ''[=AT40=]'' in 1988;
* {{MTV}}'s (later {{VH1}}'s) ''Top 20 Video Countdown''.

Apart from first-run airings with Seacrest, Kasem-era reruns of the program, ''Casey Kasem's American Top 40: The '70s/'80s'', are also syndicated weekly.

!!"The tropes from coast to cooooooast!":
* AudienceParticipation: You can vote for your favorite song at [[http://www.at40.com the show's official website]]; the results will be factored into the countdown.
** The "Long Distance Dedication" was added in 1978 to make the show more interactive.
* {{Bowdlerization}}: [[ChuckBerry Chuck Berry's]] "[[IntercourseWithYou My Ding-A-Ling]]" was replaced with a different song in several markets when it reached #1 in 1972, and reruns of those weeks' programs have featured a different song in the #1 position in certain markets.
** To clarify, the show itself never removed any songs from the countdown because of content concerns, but allowed local stations to do so if they wanted. They also occasionally created their own in-house edited versions of songs, for content or time purposes (or both, sometimes). Most infamously, they edited "Mind Playing Tricks on Me" by GetoBoys down to a little over one minute.
* CatchPhrase: "Keep your feet on the ground, and keep reaching for the stars!" in the Kasem years.
** "''American Top 40'' originates from Hollywood", or a variation.
** "I'm Casey Kasem."
** "And the countdown continues/rolls on."
** "Up ___ big notches to number ___."
* DramaticTimpani: A drumroll was used before Kasem announced the week's No. 1 song. A longer one was used on year-end programs, before revealing the year's No. 1 song.
* EarlyInstallmentWeirdness: ''America's Top 10'' started out as a faux newscast, with Casey actually sitting behind an anchor desk. After a few shows they switched to a more relaxed style with Kasem sitting cross-legged in a comfortable-looking chair.
* TheEighties: When the show was arguably at the height of its power, although it actually started in TheSeventies.
* InvincibleHero: In certain eras when a new song by certain artists debuted you could count on it eventually hitting the Top 5 if not #1. Even if you liked the song you had to hunker down and get ready to hear it every single week for the next few ''months'' . Good examples are anything by [[Music/TheBeeGees the Gibb brothers]] in the late 70s or Music/MichaelJackson in the 80s.
* LongList / TopTenList: Forty songs, plus a couple of extras, in four hours (originally three).
* LongRunner: The program debuted in 1970 and ran uninterrupted for almost 25 years. The current run, dating back to 1998, also qualifies.
* {{Montages}}: A staple of the year-end programs during the 1970s (1974-1978), and then again sporadically in the 1980s; this was simply the No. 1 songs during the past year, often in chronological order. Casey would tease that somewhere included was the No. 1 song of the year except for 1975, when not only were the songs not necessarily in order, but the year's top song (Captain and Tennille's "Love Will Keep Us Together") was not included, which Kasem pointed out shortly before playing the song.
* NothingButHits: The entire premise of the program. Averted in hindsight by the syndicated reruns, featuring hit songs of their day which have long since dropped off the charts.
* PreviouslyOn: Starting in February 1979, Kasem played back the top 3 songs from the previous week's show to [[OpeningNarration lead off the countdown]]. This segment eventually would be shortened to feature just the No. 1 song of last week, and by the end of Kasem's original run (in 1988) and on into the Shadoe Stevens-era, the host would simply announce the songs at and near the top of the charts before beginning the show.
* QuietlyPerformingSisterShow: ''Radio/AmericanCountryCountdown'' is radio's longest-running, continuously produced syndicated program, outlasting ''[=AT40=]'' (whose current run dates from 1998, the year it was UnCancelled after its first run ended in 1995).
* RearrangeTheSong: Some songs would be cut in half to control the show's running time; this typically happened to songs that were on their way down the charts.
* SpinOff: ''Radio/AmericanCountryCountdown'', a country music-version of ''[=AT40=]'' that premiered in 1973 and is still going strong today. The current host is Kix Brooks (one half of the long-running duo Brooks & Dunn); before him were original host Don Bowman (who once guest-hosted ''[=AT40=]'') and later, Bob Kingsley (the host at the height of ACC's run).
** ''Casey's Countdown'', later renamed to ''American Top 20'', even ''later'' renamed to ''American Top 10''. Hosted by Casey, all three programs were essentially ''American Top 40'' for the Adult Contemporary market. Previously, a similar program, ''America's Top 10'' (also hosted by Casey), had aired from 1980 to 1992; unlike the former shows, ''[=AT10=]'' was a music video showcase and aired on television.
* SpiritualSuccessor: ''[[DuelingShows Casey's Top 40]]'', created the year after Casey left ''[=AT40=]'' and running from 1989-1998. The program even used the "Casey's Coast to Coast!" bumper that had been present in ''[=AT40=]''.
* VocalEvolution: Casey's vocal tone shifted several times over the years, which he later acknowledged, though he said it wasn't intentional. In the first few years he had a laid-back, vaguely hipster-ish style, then shifted to a warmer, more friendly approach. His late 70s/early 80s persona has been called "Disco Casey": slick, energetic and enthusiastic. After that he settled into a more avuncular and authoritative style.
* WhatHappenedToTheMouse and ChuckCunninghamSyndrome: An occasional feature was "Whatever Happened To ... ?" where Casey would profile a one-hit wonder, or early prolific star of the rock era who suddenly disappeared off the charts, quit recording, etc. Casey would simply explain what said artist (or group, as appropriately) had been doing in recent years, if they were involved with current projects, and so forth.
** One of the most popular "Whatever Happened To ... ?" stories was of The Singing Nun, a Belgian singer christened Jeanine Deckers who recorded the French language-recorded "Dominque" and had a huge No. 1 hit in the United States in late 1963. Casey's stories on Deckers would always explain that The Singing Nun gave all royalties to the convent but later left the Catholic church in the late 1960s, and later the Belgian government made a claim for back taxes to the tune of $63,000 ... more than Deckers could afford, and no documentation existed that she had donated anything to charity. (The common stories are that her attorney failed to document it and/or that the Catholic church had either destroyed all records of it after they and Deckers broke ties, or that they simply did not have any more responsibility for her and did not have the funds.) Updated several times through the years, the final chapter came in 1985 when Casey announced that Deckers had died (of suicide) at age 51.
** Two entire specials were based on the WhatHappenedToTheMouse concept one in July 1973 and the other in April 1975 where Casey played the biggest singles by one-hit wonders during the rock era. The 1975 special had a slightly different chart, with a few different songs added and a different No. 1 song.
* WholeEpisodeFlashback: A 1975 episode, celebrating the show's fifth anniversary, was a rebroadcast of the very first [=AT40=] from July 4, 1970. The only difference was Kasem occasionally inserting a bumper reminding listeners that this was indeed a program from 1970, and pre- and post-show remarks.
* WritingAroundTrademarks: When Kasem started ''Casey's Top 40'' he was able use the same segments that he'd done on [=AT40=] but he couldn't use the same names. So for example, the "Long Distance Dedication" became the "Request & Dedication".
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-->''"Keep your feet on the ground, and keep reaching for the stars!"''