Ballard Spahr is combining with Minneapolis-based Lindquist & Vennum, the two firms announced Tuesday.

The combined firm will operate under the name Ballard Spahr, and will have more than 650 lawyers across 15 offices. The deal makes Ballard Spahr one of the five largest Philadelphia-based law firms by head count, according to The National Law Journal's rankings of the largest U.S. law firms.

Lindquist & Vennum, which has about 150 lawyers, focuses on corporate M&A, finance and litigation matters, working largely with middle-market companies. The firm has offices in Minneapolis, Denver and Sioux Falls, South Dakota.