What was the closing price for "Ameritech Corporation" (AIT) on
February 22nd, 1991?  Ameritech was one of the companies created by
the Bell divesititure.  It was eventually bought by SBC and its ticker
symbol was reused.  This makes it hard to look up in the databases I
know about.

PDKU ?

The typical sources of financial data ? BigCharts.com and Yahoo!
Finance ? don?t keep an archive of stocks that have been delisted, as
you?ve observed.

This means using another source.  The one that?s easiest to access
online is The New York Times, which is available for free via many
public libraries.  A company called Proquest provides it and it is
searchable back to 1851, even if that pre-dates both Ameritech and
Alexander Graham Bell.

Ameritech on Friday, Feb. 22, 1991 closed at 65 5/8, -3/8 in the day?s
trading on the New York Stock Exchange.  It traded 233,100 shares and
had been in a range of 52 ½ to 69 ¾ for the year.  The Dow Jones
Industrial Average on that day stood at 2,889.36, off 2.47 for the day
and a barrel of oil was $17.91.

Google search strategy:
Use Proquest Historical newspaper, search for ?stocks? to get exchange listings.  

Best regards,

Omnivorous-GA