Firstar stalks lucrative Chicago suburbs in First Colonial deal. (Firstar Corp.; First Colonial Bankshares Corp.)

By acquiring First Colonial Bankshares Corp. for $314 million, Firstar Corp. hopes to grab a chunk of the lucrative suburban Chicago market at an economical price.

On July 31, Firstar announced it intended to buy First Colonial, a move that would almost triple Firstar's Illinois assets to $2.8 billion and make it that state's seventh-largest bank holding company.

When it's completed, the acquisition -- Firstar's seventh in Illinois since 1987 -- will swell Firstar's presence in Chicago's Cook County to 1.5 percent of the market, or about $1 billion in assets, according to the Milwaukee bank holding company.

But Firstar's share of the market in Chicago's high-end suburbs will grow even more. For instance, the bank's …