President Obama surprised his wife with a 46th birthday party at one of Washington's most well-known restaurants Saturday night. 

Known for its commitment to organically grown food -- 95 percent of it is produced by organic growers -- Restaurant Nora in Washington's Dupont Circle hosted the first couple, the first lady's mother, Marion Robinson, Attorney General Eric Holder, White House Adviser Valerie Jarrett and Jocelyn Frye, who is a domestic policy adviser to both the president and first lady.

Mrs. Obama wore a dark, knee-length dress with a black overcoat on top. The coat had a goldish-metallic criss-cross pattern from about the waist down. President Obama was dressed casually with no tie.

The party lasted nearly four hours, and as the first couple was departing, Michelle Obama was treated to a round of "Happy Birthday" by about 50 bystanders standing outside the restaurant.
The Obamas waved to the crowd, which cheered as the motorcade left the restaurant.

Michelle Obama's actual birthday is Sunday, but President Obama will be traveling to Massachusetts to campaign for Martha Coakley, who is in a tough fight with Scott Brown to replace the late Sen. Edward Kennedy and retain the Democratic party's 60-vote majority in the U.S. Senate.

Last year, Mrs. Obama spent part of her birthday on a train traveling from Philadelphia to Washington as part of Barack Obama's inauguration procession.