"They picked up some trophy properties," said Malachy Kavanagh, a spokesman at the International Council of Shopping Centers, noting that Faneuil Hall and the Fashion Show Mall "attract well over 1 million people a month."

With the acquisition, General Growth will own or manage 225 malls (including Ala Moana Center). That would make it a closer second rival to Simon Property Group Inc., which operates 246 malls across the country, Kavanagh said.

The board of Columbia, Md.-based Rouse has approved the transaction, which is subject to shareholder approval. General Growth will assume $5.4 billion in Rouse debt. The deal is expected to close in the fourth quarter of this year.

"The combination of Rouse and General Growth seems like a big boost to General Growth and a nice buyout for Rouse shareholders, where debt ratings recently were on the rebound," said Richard Hastings, an analyst at Bernard Sands, a New York-based retail credit company.

General Growth will pay $67.50 per share, a 33 percent premium over Rouse's Thursday closing price and nearly 25 percent more than Rouse stock's 52-week high of $53.97.

Shares of Rouse stock soared almost 32 percent, or $16.04, to close at $66.65 a share on the New York Stock Exchange. But investors' worries about the amount of debt General Growth is assuming pushed down its shares by almost 5 percent, or $1.54, closing at $30 on the NYSE.

General Growth is borrowing $7 billion to finance the deal, pushing its debt to $23 billion, chief financial officer Bernard Freibaum said.

General Growth chief executive John Bucksbaum said during a conference call yesterday that the acquisitions would give the company a commanding presence in key markets, including Denver, Salt Lake City, Atlanta, Minneapolis and Baltimore-Washington, D.C. The deal also allows General Growth to enter the markets of New York and New Jersey.