SCBT Financial Corp., owner of Columbia’s largest publicly traded bank, and First Financial Holdings Inc., owner of Charleston’s second-biggest bank, announced Wednesday they agreed to a $302 million merger.

When the deal closes in the fall, the combined bank will be the fifth-largest in South Carolina based on deposits.

The holding company will operate under the name First Financial Holdings. A news release did not say what name the combind 148 branches in the Carolionas would use.

The banks’ boards unanimously approved the merger, according to a news release.

“Our two banks complement each other significantly and, because of our size, earnings power and strength, we will be uniquely positioned to build a premier regional bank in the Southeast,” SCBT chief executive Robert Hill Jr. said.

The merged companies said they will have about $8.3 billion in total assets, $6.9 billion in total deposits and $6.1 billion in total loans.

First Financial shareholders will receive 0.4237 shares of SCBT common stock for each share of First Financial common stock. Based on SCBT’s closing stock price of $43.18 on Tuesday, the deal is worth $302.4 million with 16.5 million shares of First Financial common stock outstanding.

First Financial chief executive Wayne Hall will become named president of SCBT Financial Corp., the news release said. Hill will remain chief executive of SCBT.

SCBT chairman Robert Horger will remain in that position. First Financial chairwoman Paula Harper Bethea will become vice chair of the board. SCBT will add five First Financial board members to the combined company’s board.