The result of that process was a sound that moved away from the purer punk rock that had characterized them. On London Calling, The Clash opened up to exploring reggae, rockabilly, ska, New Orleans R&B, pop, lounge jazz, and hard rock. The lyrics touched on themes such as social displacement, unemployment, racial conflicts, drug use, and the responsibilities that come with adulthood. The album, which was released in the UK in December 1979 and reached the United States and Canada in January 1980, had a good reception on the charts, with the title track reaching the top 20 singles.
The influence of this work is notable. It is estimated to have sold over five million copies worldwide and was recognized with platinum in the United States. Its impact is reflected in lists of the best albums of all time; for example, on Rolling Stone's list, London Calling ranked 8th in the 2003 and 2012 editions, and 16th in the 2020 edition. Even in 2010, the UK's Royal Mail commemorated it in a series of postage stamps dedicated to classic British album covers. The cover itself, designed by Lowry and photographed by Pennie Smith, is a nod to the design of Elvis Presley's first album.