The season-ending episode of Downton Abbey was a ratings success in the US, if not a fan favourite.
The Public Broadcasting Service (PBS) hit show disappointed many fans by killing off a popular character to end the third season on Sunday.
The Nielsen company said 8.2 million people saw it.
The show's third season is the most-watched series on PBS since Ken Burns' epic The Civil War, which first aired in 1990.
CBS had 15 of the 20 most popular shows on the air last week, led by The Big Bang Theory. But CBS also had a rare misstep, axeing The Job after only two episodes appeared on the air.
In further evidence of how TV viewing is changing, Downton Abbey and two programmes that aired on cable networks on Sunday - The Walking Dead on AMC (11.1 million) and the NBA All-Star Game on TNT (eight million) - had more viewers than anything on ABC, Fox and NBC that night.