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. At the time of its acquisition by Firstar, Mercantile was a $36 billion multi-bank holding company headquartered in St. Louis operating 500 locations in Missouri, Iowa, Kansas, Illinois, Arkansas and Kentucky. History In December 1964, the Mercantile Trust Company converted from a state‐chartered trust company into a national bank and was renamed Mercantile Trust Company National Association. Mercantile Trust Company formed a holding company in 1970 called Mercantile Bancorporation to allow it to acquire other banks and to expand beyond St. Louis. Upon the retirement of Donald E. Lasater in 1989, Thomas H. Jacobsen, a vice chairman of Florida-based Barnett Banks, replaced Lasater as president, chief executive, and chairman of Mercantile Bancorporation. Expansion in Missouri In November 1991, Mercantile announced the pending acquisition of the St. Joseph-based Ameribanc with its American Bank subsidiaries for $87 million in stock. The acquisition was completed in April 1992. In August 1993, Mercantile announced the pending acquisition of the St. Louis-based United Postal Bancorp with its United Postal Savings Association subsidiary for $192 million in stock. The acquisition was completed in January 1994. In September 1994, Mercantile announced the pending acquisition of the Kansas City-based Central Mortgage Bancshares Inc. for $97 million in stock. In January 1995, Mercantile announced the pending acquisition of the Springfield-based Southwest Bancshares Inc. for $23 million in stock. In February 1995, Mercantile announced the pending acquisition of the Sikeston-based AmeriFirst Bancorporation with its AmeriFirst Bank subsidiary for $23.6 million in stock. In October 1996, Mercantile announced the pending acquisition of the St. Louis-based Mark Twain Bancshares Inc. with its Mark Twain Bank subsidiary for $855 million in stock. At the time of the announcement, Mercantile had 440 branches in Missouri, Illinois, Iowa and Arkansas while Mark Twain had 39 branches in St. Louis and Kansas City areas. The acquisition was completed in April 1997. In December 1996, Mercantile announced the pending acquisition of the Chesterfield-based Roosevelt Financial Group Inc. with its Roosevelt Bank subsidiary for $1.07 billion in stock and cash.