Saul Ewing offices in Baltimore, MD.

Philadelphia-based Saul Ewing and Chicago-based Arnstein & Lehr have merged, the firms announced Tuesday, creating a firm of more than 400 lawyers with 15 offices across the Northeast, Midwest and Florida. The combined firm will be called Saul Ewing Arnstein & Lehr.

Barry Levin, managing partner of Saul Ewing, will continue to serve as managing partner of the combined entity. Jeffrey Shapiro, Arnstein & Lehr’s managing partner, will now lead the combined firm’s Miami office, and will serve on its executive committee.

The two firms confirmed in May that they were in merger talks. Their combination became official Sept. 1.

“For many years, Saul Ewing looked for the right growth opportunity that would build on our special culture and passion for putting clients first,” Levin said in a statement Tuesday. “We immediately found that same client commitment with Arnstein & Lehr.

The firms have no overlap in geographic footprint. Philadelphia-based Saul Ewing, with more than 250 lawyers, is concentrated in the Northeast, with all of its offices located between Washington, D.C., and Boston. Its westernmost office is in Pittsburgh. By adding Arnstein & Lehr’s approximately 150 lawyers, Saul Ewing would gain significant presence in both Chicago and Florida.

The two firms share several clients, their announcement said.

Saul Ewing has expanded several times through mergers with smaller firms. In 1998 it merged with Baltimore-based Weinberg & Green, which increased its head count from 159 lawyers to 222. In 2006, it grew its Washington, D.C., office by merging with Schmeltzer Aptaker & Shepard, a 17-lawyer boutique. It added a Boston office in 2011 by merging with seven-lawyer Dionne & Gass. It also acquired a small gaming firm based in Bethesda, Maryland, in 2010.

“Our combined experience, depth of talent, and commitment to serve our clients as our No. 1 priority have come together to form an even more energized, ambitious and results-driven firm,” Shapiro said in a statement.

This is a developing story.