Jeffrey Hammes' reign as chairman of Kirkland & Ellis will come to an end in February 2020, closing what will be a 10-year tenure in which he oversaw one of the largest growth streaks in the history of American law firms.

Hammes will be replaced by Jon Ballis, a Chicago-based corporate partner who has become one of the firm's best-known private equity lawyers.

"Jon is an incredible talent and has demonstrated the necessary leadership skills and business acumen to lead Kirkland & Ellis into the future," Hammes wrote in a memo released to the firm and obtained by The American Lawyer.

The memo said Ballis will serve as "chairman-elect" until the transition in 2020, and that Hammes will remain a partner at the firm following the move out of leadership.

The firm has a policy that requires members of its 15-strong global management executive committee to step down in the financial year after they turn 60.

Kirkland's revenue has nearly doubled during Hammes' tenure, from $1.625bn in 2010 to $3.165bn last year, when it climbed to the top of the Am Law 100. It has also become one of the wealthiest partnerships, with profits per equity partner rising more than 50% from $3.1m to $4.7m.

Its headcount in that span has grown by nearly 50%, from about 1,400 lawyers to nearly 2,000 as of last year. A firm spokeswoman said neither Hammes nor Ballis were available for interviews.

Ballis joined Kirkland's Chicago office – where the firm was founded and houses some 600-plus lawyers – in 2005 from crosstown rival Sidley Austin. He is a leader in the same private equity practice that Hammes was a part of before becoming a full-time leader of the business.

Hammes has also made a name for himself thanks to an aggressive style of lateral recruiting, paying top dollar to lure partners from New York's elite lockstep firms. In one of the more recent examples, Kirkland reportedly agreed to pay former Cravath Swaine & Moore partner Sandra Goldstein $11m a year for five years.

While Goldstein is a top litigator, most of Kirkland's big-ticket New York hires have been in the transactional space, where the firm has mostly focused its growth efforts under Hammes. He also focused on building the firm's public M&A practice in New York by recruiting partners from Cravath, Skadden Arps Slate Meagher & Flom, and others.

Geographically, Kirkland has also focused on expanding under Hammes' watch in some of the highest-rate cities for legal services, including London, San Francisco and Houston.

Kirkland's fastest-growing offices include London, which has grown 61% since 2013 to 189 lawyers last year; New York, where headcount is up 42% during the past five years to 503 lawyers; San Francisco, up 36% since 2013 to 126 lawyers; and Houston, where the firm now has 107 lawyers since setting up shop in 2014.

"The competition among the top-tier firms is fierce," said Kay Hoppe, a Chicago-based legal recruiter. "Hammes did a great job of putting them at the top, and Ballis will do a great job of keeping them there."