Downton Abbey, Maggie Smith and Hugh Boneville

The Season 2 finale of Downton Abbey on PBS drew a whopping 5.4 million viewers in its first airing to post the network's biggest audience in nearly three years.

The two-hour closer was PBS' most-watched program since the 2009 premiere of Ken Burns' National Parks and was also more than double the average prime-time PBS viewership.

Shirley MacLaine joins Downton Abbey

"PBS and our member stations are so pleased that such a large audience is enjoying this great work from Masterpiece," PBS president and CEO Paula Kerger said in a statement. "From viewing parties to Twitter mentions, Downton Abbey is riding a wave of public enthusiasm, and it's been wonderful to see so many people discovering public television as a destination for programming that's smart, distinctive and entertaining."

Overall, Season 2 was up by 25 percent over the first season.

Season 3, which will feature new cast member Shirley MacLaine, is currently in production in England and is scheduled to hit stateside early next year.