But this didn’t seem right to James McGrath Morris, who began working on a biography of Pulitzer a decade ago. Pulitzer was a deliberate, calculating man; impulse purchases weren’t part of his modus operandi.Mr. Morris suspected that one place to look for countervailing evidence was the arrival notices that 19th-century newspapers would print whenever someone significant checked into a local hotel — a forerunner to the tweet, enabling friends to know someone was in town and where to find them. If Pulitzer visited New York City to check out takeover targets prior to 1883, he might surface in these mundane social announcements. The problem was, The New York Times and other papers...