In another win for Liam Neeson and his adult fans, Warner Bros. and Dark Castle Entertainment's action-thriller Unknown scored a surprise victory in besting Alex Pettyfer teen sci-fi adventure I Am Number Four at the President's Day box office.

But overall, the downturn at the domestic box office continued, with revenues off 30% from President's Day weekend last year (which fell a week earlier).

Unknown opened to an estimated $21.8 million from 3,043 theaters through Sunday, according to Rentrak. It's on target to gross around $26 million for the four-day holiday weekend. A resounding 89% of the audience was over the age of 25 -- and 54% over the age of 50.

Neeson scored a similar victory with Taken, distributed by Fox. Unknown, which cost $30 million to produce, was fully financed by Joel Silver's Dark Castle. The film also stars Diane Kruger and January Jones.

"I'm happy for Joel to have a breakout film. Dark Castle has struggled at the box office the past couple of years, and this helps turns things around," Warners president of domestic distribution Dan Fellman said. "We were up 32% on Saturday, which is a big jump for an adult movie. People really liked it."

DreamWorks and Touchstone's Number Four  opened to a softer-than-expected $19.5 million through Sunday to come in No. 2 for the three days, but not by much.

Holdover family toon Gnomeo & Juliet--also from Touchstone--grossed $19.4 million for the three days, and should overtake Number Four on Monday to end the holiday weekend at No. 2, behind Unknown.

Imax theaters contributed $2.6 million of the three-day gross for Number Four.

Hollywood studios have been complaining for months about tracking, and President's Day weekend was no different. Going into the holiday, tracking services mistakenly showed Number Four in the lead on the strength of younger moviegoers, and especially teenage girls.

But that support didn't fully materialize, with 54% of Number Four's audience over the age of 25. Just as problematic, 57% of those going to see the film were males. Pettyfer, still a relatively unknown commodity, was expected to draw younger women and teenage girls. The film also stars Glee's Dianna Agron and Teresa Palmer. Overseas, Number Four grossed $3.3 million as it opened in eight smaller territories.

Number Four, directed by D.J. Caruso (Disturbia), is the first film from a reconstituted DreamWorks, and is the first to be released by Touchstone under DreamWorks' output and marketing deal with Disney. Movie cost $50 million to produce.

"It was an extremely competitive weekend, and we still have two days [Sunday and Monday] to see how all the films play out," said Disney worldwide president of distribution Chuck Viane, noting that Number Four should have good legs going forward.

Gnomeo came in a pleasing No. 3 for the three-day weekend, grossing $19.4 million from 3,013 theaters for a cume of $50.4 million through Sunday, it's 10th day in release.

With families available on Monday because of the holiday, Gnomeo is projected to gross roughly $25.3 million for the four-day weekend, while Number Four is projected to gross around $22 million or $23 million.

Also holding well in its second weekend, Sony's Adam Sandler-Jennifer Aniston romantic comedy Just Go With It grossed $18.2 million from 3,548 theaters for the three-day weekend to come in No. 4. It's possible Go With It could beat Number Four for the four days, but most give an edge to the latter.

Go With It -- sporting a domestic cume of $60.8 million through Sunday -- points to Sandler's staying power at the box office.

New Regency and 20th Century Fox's franchise relaunch Big Mommas: Like Father, Like Son came in No. 5 in its debut, grossing an estimated $17 million through Sunday as it opened in 2,821 theaters. Total gross for the four-day weekend is projected at $20 million.

All three new films -- Unknown, Number Four and Big Mommas -- received a B+ CinemaScore.

There's another thing the trio share in common. All were released by major studios, but financed and produced by outside companies.

Big Mommas, starring Martin Lawrence and Brandon T. Jackson, played heavily to African-Americans, who made up 66% of the audience. It also did well with Hispanics, who made up 21% of those buying tickets.

"The film is getting everyone -- males, females, young, old and families," Fox executive vice president of distribution Bert Livingston said.

Coming in No. 6 was Paramount's Justin Bieber: Never Say Never, which held better than expected in its second weekend. Movie declined 54% for the three days to an estimated $13.6 million for a cume of $48.5 million through Sunday.
Never Say Never could earn another $3 million on Monday, putting it's cume at north of $50 million.

With one week left to go before the Academy Awards, both The King's Speech and Black Swan jumped the $100 million mark domestically. King's Speech came in No. 7 for the weekend.

Sony's The Roommate came in No. 8 for the three days, grossing an estimated $4.1 million from 2,160 locations for a cume of $32.7 million in its third frame.

Focus Features' Channing Tatum Roman epic The Eagle slipped 59% to an estimated $3.6 million from 2,296 for a cume of $15.1 million in its first 10 days. Pic placed No. 9.

Rounding out the top 10 chart was Paramount and Spyglass' Natalie Portman-Ashton Kutcher romantic comedy No Strings Attached, which grossed an estimated $3.1 million from 1,966 locations for a cume of $66 million in its fifth weekend.

On the specialty side, National Geographic documentary The Last Lions scored the top location average of the three-day weekend, grossing an estimated $46,000 as it opened in four theaters for an average $11,500. Documentary was narrated by Jeremy Irons and directed by Dereck and Beverly Joubert.

Fox Searchlight's offbeat comedy Cedar Rapids grossed nearly $1 million as it expanded to 102 theaters in its second weekend for a theater average of $8,909 and cume of $1.5 million.

Full numbers for President's Day weekend will be out Monday morning.