Daniel M. Gallagher was sworn in Monday as the fifth commissioner of the Securities and Exchange Commission.
Mr. Gallagher replaces Kathleen Casey, who left in August. His term runs five years.
He first worked at the SEC in 2006 as counsel to then-Chairman Christopher Cox. He also worked in the division of trading and markets, where his duties included helping to formulate the SEC's response to the financial crisis. He joined the Washington law firm of WilmerHale in 2010 as a partner.