United Bankshares Inc. /zigman2/quotes/202436974/composite UBSI +1.33% announced Monday a deal to buy Carolina Financial Corp. in a stock deal valued at $1.1 billion. Under terms of the deal, each Carolina Financial share will be exchanged for 1.13 United Bankshares shares. Based on Friday's stock closing prices, that values Charleston, South Carolina-based Carolina Financial shares at $44.65, or a 15.7% premium, and implies a market capitalization of about $993.4 million. The deal will result in a bank with combined assets of $25 billion. Shares of the regional banks are still inactive in premarket trading. Washington, D.C.-based United Bankshares' stock has rallied 27.0% year to date and Carolina Financial shares have run up 30.4%, while the SPDR S&P Regional Banking ETF /zigman2/quotes/200108291/composite KRE +1.07% has climbed 19.6% and the S&P 500 /zigman2/quotes/210599714/realtime SPX +1.59% has advanced 24.5%.