Mercantile Bancorporation was the largest bank holding company in Missouri when it was acquired by Firstar Corporation in 1999. The Mercantile Bank of St. Louis was founded in St. Louis, Missouri, in 1850. In 1996, its chief executive Thomas H. Jacobsen began a series of acquisitions, increasing its assets from $15.9 billion to $35.8 billion. One of the biggest acquisitions was that of Mark Twain Bancshares in 1996.