Peter Mills Mattoon, 84, of Lafayette Hill, chairman of Ballard Spahr for more than 16 years as the firm grew in prominence in the 1980s and 1990s, died Tuesday of injuries sustained in a fall.

In a tribute, Ballard Spahr described Mr. Mattoon as a dignified man of few words, almost none about himself.

“Peter had that character, that presence,” said Robert McQuiston, a retired Ballard Spahr partner. “He was just so sound, so solid, so deliberative.”

John Langel—who Mr. Mattoon hired, mentored in sports law and eventually tapped to form the firm’s labor and employment practice—said he made his partners see the importance of working together through his "one-firm firm" philosophy.

“To Peter, 'one-firm firm' did not mean complacency,” Langel said. “I first heard from Peter the concept that we were falling behind if we were doing today what we did yesterday.