Crown Castle today said it is buying tower company Mountain Union Telecom for $309 million, gaining the company's 547 sites in California, Nevada, New Jersey, Pennsylvania and Puerto Rico.

Already one of the largest tower operators in the U.S., Crown Castle will bulk up its portfolio with the acquisition, especially in high-value markets like Las Vegas and Los Angeles where Mountain Union runs dozens of towers. Crown Castle currently owns, operates and manages 11,000 towers in the U.S. and 1300 in Australia, and in the U.S. it has coverage in 76 of the top 100 markets, but most of its properties are concentrated east of the Mississippi river.

Crown Castle expects to close the deal July 1, acquiring 98% of all outstanding equity in Mountain Union for $304 million in cash and reserving the right to buy the remaining 2% of the company in 2007 for $5 million.