New York City-based Tiedemann Wealth Management will merge with San Francisco-based Presidio Capital Advisors, the firms announced on Monday. The transaction enables Tiedemann to instantly become a major force in northern California, a market it had targeted for expansion.

Presidio Capital Advisors will adopt the Tiedemann Wealth Management branding. The combined firms will oversee $13 billion in client assets and operate out of offices in New York, San Francisco, Dallas, Washington, D.C., Palm Beach, Fla. and Wilmington, Del.

"The firms and the people involved all know each other, like each other and complement each other," says Craig Smith, president of Tiedemann Wealth Management. "We share common values, a client focus, and objectivity, and we're really excited about combining our talent pools to create something broader and more diverse."

Both firms target ultra-affluent clients. According to Financial Advisor's RIA survey, Tiedemann's average client had about $34 million in assets at the firm. while Presidio's had $22 million.

Tiedemann had $9 billion AUM at the time of the merger. Its CEO, Michael Tiedemann, and president, Craig Smith, will remain in their roles.

“This is a very positive development for our clients who will benefit from the resources and expertise of two of the country’s leading investment and wealth advisory firms. We are now on the ground in the financial, technology, energy and political centers of the U.S.,” said Tiedemann in a released statement. “Tiedemann and Presidio share a single focus: partner with clients to provide them with objective advice and protect and grow their wealth for generations.”

Presidio Capital Advisors, a subsidiary of The Presidio Group, managed approximately $4 billion in client assets at the time of the merger.

Brodie Cobb, founder and CEO of The Presidio Group, will join Tiedemann’s board of directors.

“We are proud to join forces with a firm that shares our values of accountability, transparency and focus on results, along with the same dedication and passion to a high-touch, clients-first approach,” said Brodie Cobb, Founder and CEO of The Presidio Group in a statement. “This partnership enables us to provide our clients with deeper and expanded investment, estate planning and trust resources and services.”

The merger was advised by Silver Lane Advisors. Terms of the deal were not disclosed.