She will join a small group of women in the United States who have headed large law firms, including Nina Gussack, the chair of Center City's Pepper Hamilton L.L.P. until former FBI Director Louis Freeh took over last year, and Christine Lagarde, the former chair of Baker McKenzie, who now is head of the International Monetary Fund. New York's Akin Gump Strauss Hauer & Feld L.L.P. is headed by Kim Koopersmith.
Milone became chairman of Morgan Lewis in 1999, spearheaded its growth in the United States and abroad, and helped shepherd the firm through the severe downturn in the legal market in 2008 and 2009.
The firm sharply reduced hiring for a time but has resumed its expansion, growing to about 1,400 lawyers.
McKeon said in an interview that the financial downturn, which has proven traumatic for much of the legal industry, spurred the firm to make adjustments such as moving away from the hourly billing model that had dominated firms for generations toward flat fees and other arrangements that stressed productivity.
She said the changes bolstered Morgan Lewis's underlying business and benefited clients.
"The fiscal downturn came and a lot of firms saw that as a negative," said McKeon, a graduate of Villanova University Law School. "We really looked at it in another way and saw it as an opportunity to be innovative and creative."
Milone lauded the change, saying McKeon would be an asset as leader of the firm.
"I am very excited," Milone said. "It's a great thing for the firm. She is terrific, highly energetic, and an inspiration."
McKeon, 56, lives in Wayne with her husband, John F. Hollway, and their four children. Hollway is an associate dean at the University of Pennsylvania Law School and executive director of the new Quattrone Center, which focuses on the functioning of the criminal justice system.
McKeon takes over Morgan Lewis during a time of ongoing upheaval in the once-staid legal profession.
Big firms such as Morgan Lewis still are adjusting to the legal market downturn that began with the financial crash of 2008. While many, including Morgan, have come back, the landscape appears to many observers to have been irreversibly altered.
While costs have continued to creep up, revenue has remained largely flat, forcing a fierce competition among firms for work.
Many, like Morgan, have expanded their international footprint in response, focusing on London, a base for transactional practices, or more exotic locales, such as Almaty, Kazakhstan, where Morgan has opened a thriving energy practice.
"Our international expansion has never been because we wanted to call ourselves an international firm," McKeon said. "Our expansion has always been based on where our clients are asking us to practice."
McKeon said she would continue to practice as she led the firm.
Milone, who as chair has focused full time on managing the firm, said he would be deeply involved in the transition.
Milone, 66, has helped oversee the opening of 13 of Morgan Lewis's 25 offices during his time as leader. A graduate of the University of Pennsylvania Law School, he joined the firm in 1977 as an associate and was made a partner four years later, spending much of his career in the firm's labor and employment practice.
He served as manager of the practice for a time and was managing partner of the firm before he was elected chairman.
During the financial crisis, Milone spoke candidly about the pressures that law firms faced from clients who were concerned about costs and high salaries for young associates. Since then, Milone said, a key challenge has become finding and adequately compensating young lawyers even in the face of client demands for ever-greater cost-consciousness.