One of West Virginia's largest banks, United Bank is older than the state itself. It originated as the Northwestern Bank of Virginia, founded in 1817 in Wheeling with branches in Wellsburg, Morgantown, and Clarksburg. Virginia legislative reforms allowed an additional branch to be established in 1839 in Parkersburg. Shortly afterward, another branch was established in Jeffersonville (now Tazewell), in southwestern Virginia. After the outbreak of the Civil War, the Virginia legislature split off the Jeffersonville branch. The National Banking Act of 1864, designed to create a uniform currency in the United States and to facilitate the sale of government bonds, was amended in 1865 to allow state banks to become national banks. The Wheeling branch of the Northwestern Bank was reorganized as the National Bank of West Virginia, and the Parkersburg branch became the First National Bank of Parkersburg.

The First National Bank of Parkersburg is the direct parent of United Bank. It grew through the remaining years of the 19th century into the 20th century. In 1935, it was one of the largest national banks in West Virginia. By the 1960s, it was one of the 12 largest, and it was one of the five largest banking institutions in West Virginia in the 1980s. Legislation controlling bank expansion was relaxed in West Virginia in the early 1980s and the Parkersburg National Bank became part of United Bankshares Holding Company, which included Union Central National Bank and United National Bank. In 1985, these banks were renamed United National Bank.

In 1986, United National joined forces with InterMountain Bankshares and its subsidiary, Kanawha Banking and Trust. In 2002, United National Bank converted to a state charter, becoming United Bank. In 2005, United Bankshares, with $6.4 billion in assets, was the largest bank headquartered in West Virginia, and the second largest of all banks operating in the state. United was also the largest company of any sort headquartered in West Virginia. In 2019 United Bankshares merged with Carolina Financial Corporation, the parent company of CresCom Bank. As of 2024, United Bankshares had approximately $29 billion in assets and nearly 250 locations in West Virginia, Virginia, Maryland, Ohio, Pennsylvania, North Carolina, South Carolina, and the District of Columbia. The bank has dual headquarters in Washington, D.C., and Charleston. It is the largest bank headquartered in West Virginia and, behind Truist, is the second largest bank operating in the state.

United Bank is a contributor to The West Virginia Encyclopedia.