One of the oldest law firms in Minneapolis, Mackall Crounse & Moore, is combining operations with the Madison, Wis.-based firm DeWitt Ross & Stevens. The arrangement, announced Monday, becomes official on Nov. 16.

The 26 attorneys at Mackall Crounse will become part of the larger DeWitt Ross firm, which has 81 attorneys and an additional office in Milwaukee.

The new firm will continue to be headquartered in Madison and the existing management structure at DeWitt Ross & Stevens will remain in place.

The Minneapolis office will be known as DeWitt Mackall Crounse & Moore. The Wisconsin offices will continue to go by DeWitt Ross & Stevens.

The DeWitt-Mackall combination is the latest legal move in the Twin Cities that provides an outside firm with a foothold in the market.

In September, the Minneapolis firm Leonard Street and Deinard announced that it is merging with the Kansas City, Mo., firm Stinson Morrison Hecker effective Jan. 1, 2014. Two years ago, in a blockbuster move, the Twin Cities firm Faegre & Benson merged with the Indianapolis firm Baker & Daniels to become Faegre Baker Daniels.

"This move is consistent with the Faegre and Leonard Street and Deinard mergers; all three seek to expand its Midwest footprint," said Minneapolis legal consultant Roy S. Ginsburg.

Ginsburg said legal economics can be challenging for small and midsize firms as "baby boomer leaders and rainmakers" retire and leadership succession plans get muddled.

Robert Due, the managing partner for Mackall Crounse & Moore, was not available for comment.

On its website, the firm said of the transaction, "Our attorneys made the decision to grow and provide clients with an enhanced value proposition."

Leaders of both firms have known each other for a decade as members of a legal referral network for small and midsize law firms called Lexwork International.

The Mackall Crounse website said the combined firm will provide its existing clients with greater legal services and efficiencies that accompany a firm of more than 100 lawyers.

"Our expansion into the Twin Cities region is strategic,'' Bradley Raaths, managing partner of DeWitt Ross, said in a statement. "We are extremely excited about our growth and the opportunities this combination presents to both our attorneys and clients.''

Mackall Crounse & Moore was founded in 1918 and became known for its practices in corporate, banking, tax, estate planning, mining and litigation.

DeWitt Ross & Stevens was founded in 1903 and has practice strengths in corporate, environmental, government relations, labor and management, intellectual property and litigation areas.

DeWitt's client list includes banks, trucking interests, mining companies and manufacturers. Mackall represents ­several Fortune 500 companies as well as lending institutions.