The Carnival Films show, which airs on Masterpiece on PBS in the country, reached an average of 12.3 million viewers, with the entire third series averaging 11.5 million viewers.
It has become the highest-rating TV drama in PBS's history, and has reached over 24 million viewers overall.
The numbers for the program - written by Julian Fellowes and executive produced by Gareth Neame, Liz Trubridge and Julian Fellowes - see a seven million increase on the US ratings for series two.
Over the course of the three series, Downton Abbey has won nine Emmys, three Golden Globes and, most recently, the SAG Award for 'Outstanding Ensemble Cast in a Drama Series'.
Read more: http://www.digitalspy.com/tv/s183/downton-abbey/news/a466910/downton-abbey-breaks-us-television-record.html#ixzz2O5YFZws2
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