Solis, a former California congresswoman, was the nation's first Hispanic labor secretary. She expected to return home to California to run for a seat on the Los Angeles County Board of Supervisors.
A White House official said Attorney General Eric Holder, Health and Human Services Secretary Kathleen Sebelius and Veterans Affairs Secretary Eric Shinseki would stay on as the second term begins. It would ensure diversity among the president's leadership team -- Holder is black, Sebelius is a woman and Shinseki is of Japanese-American descent.
Some Democratic women have raised concerns that the "big three" jobs in the cabinet -- State, Defense and Treasury -- will be taken by white men. Terry O'Neill, head of the National Organization for Women, said she was "disappointed so far" by the president's selections.
Sen. John Kerry (D-Mass.) has been tapped to be the next secretary of state; former Nebraska Sen. Chuck Hagel, a Republican, was picked to run the Pentagon and White House chief of staff Jack Lew is expected to be named treasury secretary later this week.
The White House is expected to announce more members of Obama's cabinet in the coming weeks.
Environmental Protection Agency Administrator Lisa Jackson said last month she is stepping down after nearly four years as the administration's chief environmental watchdog. Energy Secretary Steven Chu, meanwhile, is expected to leave sometime after the inauguration, while Interior Secretary Ken Salazar's plans are unknown.
The only Republican in the cabinet, Transportation Secretary Ray LaHood, has not indicated whether he will leave the administration.