First Lady Michelle Obama spoke about community service, helping others and overcoming obstacles when she addressed 550 Spelman College graduates Sunday in College Park.

"Do big things," she told her audience. "Now it's your turn to repay the favor."

Obama delivered her keynote speech to 9,000 people in the ballroom of the Georgia International Convention Center, saluting the graduating class for one of the nation’s two historically black women’s colleges.

“It is vitally important that you all rise to the highest ranks of every industry and every profession,” Obama said. “As you climb those career ladders, just remember to reach down and pull others up behind you.”

Obama recounted how she took a high-paying job in the high-rise offices of a Chicago law firm. While she welcomed the paycheck, and paying down her student loans, she missed doing more fulfilling work.

“Much to the surprise of my family and friends, I left that high-paying job,” she said. “I was making a lot less money and the office was a lot smaller. But I woke up every morning with a sense of purpose and possibility.”

Obama discussed the college’s improbable founding in 1881 by two white women from the north, with an initial class of 11 women of varying ages in a room lent by a church, many of them former slaves.

Grass grew on the floor after it rained. There was barely enough light to read by.

“But still, week after week, more women showed up to enroll; some walked eight or nine miles each way,” Obama said. “That tenacity has defined Spelman women.”

As Obama walked on stage, those in the ballroom stood and roared.

Several people arrived as early as 11:15 a.m. to get seats up front. Others found seats at the back of the hall at 1:45 p.m. after getting in line at noon.

Kiara Ramey, 17, came to see her older sister Karonda Foster graduate. She was impressed with the first lady's nutrition initiative, which has taught her that "you can do anything."

Graduate Candice Cannon, a political science major, said the experience was surreal. She also was at the inauguration, but said Michelle Obama's speech meant more to her for its recognition of Spelman.

"African American women never imagined themselves being in her position," Cannon said.

Getting the first lady to speak at its graduation was a coup for the tiny Atlanta women’s college. Obama apparently was swayed by a letter-writing and video campaign by current and former students -- the latter including her trip director Kristen Jarvis -- and Spelman College President Beverly Tatum.

“Kristen is my right-hand woman,” Obama said of Jarvis. “She travels with me all across the country and around the world. I want to thank Spelman for giving me Kristen.”

Obama picked four schools, including Spelman, to address at graduation this year. She already had spoken to the University of Northern Iowa, in a state considered a key battleground her husband’s reelection. She will address the U.S. Military Academy graduates at West Point, and the 26 graduating seniors of Quantico Middle High School, whose parents serve at the Quantico Marine Base in Virginia.

Obama wasn’t the only celebrity figure to receive applause at Spelman’s ceremony. Director and choreographer Debbie Allen, actress Phylicia Rashad and Wendy Kopp, chief executive officer of Teach For America, were given big ovations when they received their honorary doctorates.

Mayor Kasim Reed, former Atlanta Mayor Shirley Franklin, U.S. Senator Johnny Isakson, R-Ga., and Congressman Hank Johnson also attended the event.