When Mark Twain visited in 1884, he claimed to spy a little bit of hell in Pittsburgh's smoky appearance. Twain's observations are among the many riveting firsthand accounts and anecdotes to be found in the archives of the Pittsburgh Post-Gazette. The Great War hit home after the sinking of the Lusitania, which carried more than a dozen Pittsburgh residents. A few years later, cheering throngs of black and white residents lined downtown streets to welcome African American soldiers returning home from the conflict. The Ringling Brothers Circus held its last outdoor performance here in 1956 and...