Environmental Protection Agency administrator Lisa Jackson on Thursday announced that she would be stepping down from her post, the Associated Press reports.
Jackson's resignation marks the end of a tenure at the EPA that spanned almost four years. She was the first African-American to head the agency.
A frequent target of Republican criticism, Jackson offered no specific explanation for her resignation.
"I will leave the EPA confident the ship is sailing in the right direction, and ready in my own life for new challenges, time with my family and new opportunities to make a difference," Jackson said in a statement.
Jackson will officially step down after President Obama's State of the Union address next month.