Education for girls is the central theme of the first lady's trip, which also includes stops in Morocco and Spain.
Liberia was battered by civil wars between 1989 and 2003.
Then Ebola swept the country in 2014, killing more than 4,800 people. Teachers died and schools were closed for months.
The country was founded as part of an effort to resettle freed American slaves and has deep ties to the United States. The country’s oldest vocational high school, located in Kakata, is named for the African-American civil rights activist Booker T. Washington.
Schools in Liberia suspended mid-term exams scheduled to start Monday “to allow the students to give Mrs. Obama a rousing welcome to appreciate what the United States has done for us,” principal Harris Tarnue said.
“She will be a real inspiration to the young girls around here,” he said.
Mrs. Obama’s previous visits to Africa as first lady have included Ghana, South Africa, Botswana, Senegal and Tanzania.