Elaine Greenberg, head of the U.S. Securities and Exchange Commission enforcement unit that polices the $4 trillion municipal securities market, is leaving the agency for private industry.

Greenberg, who joined the SEC’s Philadelphia regional office in 1987, has led enforcement actions related to municipal securities offerings against the states of New Jersey and Illinois as well as the city of Harrisburg, Pennsylvania, the SEC said in a statement today.

“Elaine’s leadership of the unit and her efforts on behalf of investors have been groundbreaking and have had a tremendous impact on the behavior of participants in the municipal securities and public pensions markets,” SEC Commissioner Elisse Walter said in the statement.

Under her leadership, Greenberg’s unit also brought cases over bid-rigging and pay-to-play schemes, the SEC said.