Both firms voted on Saturday to form a 750-lawyer practice, making it the 11th largest in the US in terms of numbers. The merger takes effect immediately and the new firm is called Piper Marbury Rudnick & Wolfe.
The combined firm has offices in Chicago, Baltimore, Washington DC, New York, Tampa, Philadelphia, Dallas and Reston, Virginia.
Rudnicks managing partner Lee Miller, is co-chairman of the new firm along with Pipers chairman Francis Burch. Jeffrey Liss, a partner at Pipers' Washington DC, office will be chief operating officer.
Miller says: "We want to build a law firm that has a strong presence in major cities and leading practitioners in a wide variety of legal practices.
"The firm will have entrepreneurial drive and the flexibility to change and grow in the new economy."
Rudnicks is best known for its property and distribution law practices, while Pipers' strengths are in corporate, litigation and regulatory