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Investor Presentaiton

Strategic Rationale Strategic Rationale Expands combined company footprint across the Greater Bay Area, Sacramento and Amador regions • Creates a $4.0 billion bank that is well positioned to become the preeminent business bank serving Northern California Increases efficiency and spreads costs across a diversified geographic footprint Increased capital enhances lending capabilities for American River Bank customers Builds immediate scale in highly attractive Northern California markets Combined company would be one of the largest community banks by market capitalization headquartered in Northern California (1)(2) American River Bank is a high quality, relationship-based business bank Community-focused bank headquartered in the Greater Sacramento region Total assets of $916 million, total loans of $475 million and total deposits of $789 million Disciplined credit and risk management cultures Aligned loan and deposit strategies allows for a seamless integration of business models Enhances already strong core deposit base Similar cultures committed to providing exceptional client service and dedication to local communities • 14.2% accretive to 2022 earnings per share (fully phased-in cost savings) Financially Attractive • 3.9% tangible book value dilution with a 3.5 year earnback • >15% internal rate of return Bank of Marin Bancorp American River Bankshares €2 Robust pro forma capital ratios (1) Includes banks with less than $10 billion in assets headquartered north of Ventura, Los Angeles, and San Bernardino counties. (2) Market data as of 4/16/2021. 3

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