[used to be] Peoples Savings Bank

The Peoples Savings Bank is now a First National Bank.

[used to be] Union National Bank

The Union National Bank is now offices for other companies.  I love the N in this font!

[used to be] Commonwealth Trust Company

The Commonwealth Trust Company building is now offices for other businesses.

[used to be... and still is] Dollar Savings Bank

While not a building that used to be something else, the Dollar Savings Bank on Fourth Ave is still the Dollar Savings Bank (a.k.a. Dollar Bank).

[used to be] Commemoration of building destruction

While not a building that used to be something else, there is a plaque in Pittsburgh commemorating the edge of where the Great Fire of Pittsburgh stopped.