NEW YORK (AP) – The National Association of Securities Dealers, which oversees the Nasdaq Stock Market, has agreed to sell the century-old American Stock Exchange for $110 million to a Chicago-based private-equity firm, officials said Monday.

The NASD signed a document Friday to sell the Wall Street-based Amex market to the private-equity firm GTCR Golder Rauner LLC after nearly a year of talks.

“I am thrilled to have a strategic investor like GTCR to support the growth of the Amex,” American Stock Exchange chairman and chief executive officer Salvatore Sodano said Monday.

“As an independent entity, the Amex will be better suited to be a leader within a changing marketplace.”

The Wall Street Journal first reported the deal Monday.

Robert Glauber, chairman and chief executive of NASD, said the deal would enable it to “focus our entire organization on NASD’s core mission of promoting market integrity and protecting investors.”

Collin Roche, a principal at GTCR, said the firm believed “Amex has strong opportunities to grow in its existing product classes while also introducing new products.”

The NASD acquired the Amex in 1998 when its leaders felt the open-outcry auction system used at the Amex would complement the electronic trading system used by the Nasdaq.

But the Amex has lost business in recent years and some of the securities that it traded are now also traded elsewhere.

NASD chairman Robert Glauber announced he wanted to sell the Amex shortly after becoming the NASD chief late in 2000.

The deal is subject to approval by the NASD’s board of governors, the Amex members and the Securities and Exchange Commission and could take months to complete, the newspaper said.

In addition to its stock business, which ranks third behind the New York Stock Exchange and Nasdaq, Amex is well-known for its trading of options.