Windes & McClaughry Accountancy Corp. of Long Beach has signed an agreement to merge with Burr Pilger Mayer Inc. of San Francisco, creating what is being billed as the largest California-based accounting and consulting firm.

The merged companies will be known as BPM Windes in Southern California and BPM in Northern California when the deal closes, which is expected by Jan 1.

Windes & McClaughry employs about 140 people and has three offices in Los Angeles County and one in Orange County. Burr Pilger Mayer employs 410 people at six offices in the Bay Area and one in Hong Kong. The two firms combined will have $100 million in revenue.

“This is the first true north-south merger of significant firms in California accounting history,” said Steve Mayer, Burr Pilger Mayer managing partner, in a statement. “Windes has a robust 85-year history in Southern California that we are looking forward to leveraging.”

Mayer will be chief executive after the merger. John Di Carlo of Windes & McClaughry will stay as managing partner, overseeing Southern California operations.

Windes is known for its state and local tax compliance and planning; estate, gift and trust planning; and third-party plan administration of qualified retirement plans. Burr Pilger Mayer is known for its SEC and international tax practices, as well as business valuation, litigation support and wealth management.