Despite blustery weather, a crowd estimated to number as many as 1.8 million people gathered on the National Mall in Washington, D.C., on Jan. 20, 2009, to witness and celebrate the inauguration of Barack Obama as the 44th president of the United States.

At 11:19 local time, just minutes before security gates to the Capitol grounds closed, the GeoEye-1 satellite captured the unprecedented moment in history from its orbit 423 miles above Earth at a position nearly 200 miles west of Washington, D.C. The massive individual concentrations of people easily identifiable in the image correspond to the positions of numerous JumboTrons placed up and down the Mall.

How Large Was the Crowd?
Although the National Park Service claims it will not dispute crowd estimates of 1.8 million, not all agree. According to a Jan. 20 CNET News report, Steve Doig, an Arizona State University professor who specializes in crowd counting, analyzed the GeoEye-1 image and estimates there were about 800,000 people in attendance.
Doig says it's simple math—dividing the square footage"by some number of square feet per person. "A scary mosh pit is 2.5 square feet per person," he explains. “That's about as tight as you can pack people, where they can't move—elevator tight." He says if people up and down the Mall were packed in that tight, there could have been 2 million.

Conversely, CNET also reports that Farouk El-Baz, a Boston University professor who is considered a leading authority on providing crowd estimates, says in an e-mail that the crowd could number "nearly 3 million people." Nearly everyone agrees it is the largest gathering ever on the National Mall.