Thriller "Unknown" found plenty of friends over the four-day, President's Day holiday weekend in the United States, as it claimed the top spot on box office charts during a slow period in movie theaters.

"Unknown," starring Liam Neeson as a man who must reclaim his identity after finding it stolen when he awakens from a coma, raked in $25.6 million over the four days starting on Friday, according to studio estimates released on Monday.

It beat family animated film "Gnomeo and Juliet," which claimed the No. 2 spot with $24.8 million, switching places from Sunday's estimates with thriller "I Am Number Four, which landed at No. 3 after four days with $22.6 million.

On Sunday, studio estimates put "Gnomeo" in the No. 3 spot with a three-day weekend total of $19.4 million to $19.5 million for "I Am Number Four." But those totals were revised downward and Monday's holiday was expected to boost the number of families in theaters, which was seen as helping "Gnomeo."

The comedy about garden gnomes in a family feud, experienced a slight 24 percent drop in ticket sales from its debut last weekend. Typically, a major studio release like "Gnomeo" might be expected drop around a 50 percent in its second weekend, but the family film has been helped by generally good critics' reviews and audience ratings.

The holiday's No. 4 movie was comedy "Just Go With It" starring Adam Sandler and Jennifer Aniston. Its four-day ticket sales were estimated at $21.7 million and it's total box office at $64.3 million in the United States and Canada.

Last week's No. 2 movie, "Justin Bieber: Never Say Never," a look at the life of teenage singer Bieber, fell to No. 6 with an estimate of $16.5 million over the four days. Its total domestic revenues now total $51.4 million after two weeks.

The weekend's other new major release, Martin Lawrence comedy "Big Mommas: Like Father Like Son" claimed the No. 5 spot with $19 million during the holiday weekend.

Ticket sales for all films in theaters from Friday through Monday were estimated at $174 million, down around 27 percent from 2010's Presidents Day weekend tally of $239.3 million, according to industry tracker Hollywood.com Box Office.

Other notable releases included Oscar hopeful "The King's Speech," which landed at No 7. with a four-day estimate of $7.9 million, pushing its total box office up to $104.6 million.

Rounding out the top 10 were holdovers from recent weeks: "The Roommate," "The Eagle" and "No Strings Attached" in the No. 8, 9 and 10 spots, respectively.