#1Bank of Marin Bancorp American River Bankshares Bank of Marin Expands Northern California Presence with Merger of Bank of Marin and American River Bank Investor Presentation | April 19, 2021#2Forward-Looking Statements This presentation may contain certain forward-looking statements that are based on management's current expectations regarding economic, legislative, and regulatory issues that may impact Bancorp's earnings in future periods. Forward-looking statements can be identified by the fact that they do not relate strictly to historical or current facts. They often include the words “believe,” “expect,” “intend,” “estimate” or words of similar meaning, or future or conditional verbs such as "will," "would,” “should,” “could” or “may." Factors that could cause future results to vary materially from current management expectations include, but are not limited to, the businesses of Bank of Marin Bancorp and/or American River Bankshares may not be integrated successfully or such integration may be more difficult, time-consuming or costly than expected; expected revenue synergies and cost savings from the acquisition may not be fully realized or realized within the expected time frame; revenues following the merger may be lower than expected; customer and employee relationships and business operations may be disrupted by the acquisition; the ability to obtain required regulatory and shareholder approvals, and the ability to complete the acquisition on the expected timeframe may be more difficult, time-consuming or costly than expected; natural disasters (such as wildfires and earthquakes), our borrowers' actual payment performance as loan deferrals related to the COVID-19 pandemic expire, changes to statutes, regulations, or regulatory policies or practices as a result of, or in response to COVID-19, including the potential adverse impact of loan modifications and payment deferrals implemented consistent with recent regulatory guidance, general economic conditions, economic uncertainty in the United States and abroad, changes in interest rates, deposit flows, real estate values, costs or effects of acquisitions, competition, changes in accounting principles, policies or guidelines, legislation or regulation (including the Coronavirus Aid, Relief and Economic Security Act of 2020, as amended, and the Economic Aid to Hard-Hit Small Businesses, Nonprofits and Venues Act of 2020), interruptions of utility service in our markets for sustained periods, and other economic, competitive, governmental, regulatory and technological factors (including external fraud and cybersecurity threats) affecting Bancorp's operations, pricing, products and services. These and other important factors are detailed in various securities law filings made periodically by Bancorp, copies of which are available from Bancorp without charge. Bancorp undertakes no obligation to release publicly the result of any revisions to these forward-looking statements that may be made to reflect events or circumstances after the date of this presentation or to reflect the occurrence of unanticipated events. Bank of Marin Bancorp American River Bankshares 2#3Strategic 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 $10 billion in assets headquartered north of Ventura, Los Angeles, and San Bernardino counties. (2) Market data as of 4/16/2021. 3#4American River Bankshares (NASDAQ: AMRB) Overview Branch Locations Kelseyville Clearlake Meadow Vista Lincoln BO Auburn Financial Highlights as of 3/31/2021 Balance Sheet ($mm) 101 Cloverdale Rocklin Total Assets Total Loans Eldorado Natio Ros Pollock Pines Placerville Geyserville Woodland North Highlands Citrus Folsom Total Deposits Height He 113 Tangible Common Equity EA $ 916.1 475.4 788.6 76.6 Angwin Windsor Davis Florin Profitability/Rates for the Quarter Ended 3/31/2021 (%) Sar Dixon Elk Grove Net Income ($000s) 2,647 Rohnert Park Vacaville Return on Average Assets 1.21 Napa Fairfield Galt AMRB (10) AMRB HQ Vallejo Lodi San Andreas Return on Average Tangible Common Equity 14.00 Net Interest Margin 3.58 Murphys Angels Camp Efficiency Ratio (FTE) 52.3 Martinez Pittsburg-Antioch Company Highlights • . . • Headquarters: Rancho Cordova, CA Strong NorCal presence: 10 full-service branches providing business banking services in Sacramento, Amador, Sonoma, and Placer counties Organic Growth in Current Markets: Low cost of core deposits, robust sales culture, and an extraordinary client experience Lending Expertise: Commercial real estate, small business ($1-$50mm), wholesalers/manufacturers, professionals, and property managers Relationship Banking: Customized financial services for businesses, business owners, their families and employees TCE / TA Leverage Ratio Tier 1 Risk-based Capital Ratio Total Risk-based Capital Ratio Asset Quality (%) Nonperforming Loans / Total Loans Net (Recoveries) Chargeoffs / Average Loans Allowance for Loans Losses / Total Loans (Excluding PPP Loans) Twain Yield on Total Loans 4.92 Cost of Total Deposits 0.09 Balance Sheet Ratios / Capital (%) Total Loans/Deposits 60.3 8.51 8.46 15.47 16.72 0.00 (0.06) 1.60 Market information as of 4/16/21 Deposit Market Share by County Stock Price ($) County Sacramento County Population (actual) County Active Deposit Median HHI Branches Rank ($actual) Market Market Cap ($mm) (¹) (#) (#) Deposits ($mm) Share Price / Tangible Book Value per Share (x) (1) (%) Price / 2022 EPS (x)(2) 1,564,478 $74,806 4 12 $437.3 1.05% Amador 39,554 $66,656 3 3 $133.7 16.45 Dividend Yield (%) Sonoma Placer 492,770 402,773 $90,481 2 14 $103.5 0.63 $95,803 1 21 $67.2 0.55 Bank of Marin Bancorp Source: Company documents, S&P Global, FactSet, and FDIC Summary of Deposits. Note: Deposit market share data as of 6/30/2020. Excludes non-retail deposits. Based on common shares outstanding of 5,962,466 as of 3/31/2021. Consensus estimates per FactSet. American River Bankshares (1) (2) $ 16.35 $ 97.5 1.27x 12.5x 1.71#5Greater Sacramento Region Market Highlights American River Bank expands BMRC's presence into a growing Greater Sacramento Region • • The Greater Sacramento region has a population of ~2.6 million The population of Sacramento-Roseville-Folsom MSA is expected to grow 3.6% from 2021 to 2026, compared to 2.6% for the state of California and 2.9% nationwide Additionally, household income is expected to grow 13.0% from 2021 to 2026, compared to only 9.0% nationwide In the last year, the region has been ranked the top migration destination for people looking to relocate, driven in part by newly remote workers seeking a more affordable lifestyle while still accessible to everything Northern California has to offer Ample amount of available low-rise, campus-style office space for companies to open satellite offices to follow employees migrating into the region Increasingly attractive market for companies seeking educated, young professionals from a number of universities including UC Davis, Sacramento State University, and University of the Pacific Sacramento's Downtown and Midtown areas have been experiencing a renaissance and reinvigoration $6 billion invested in new development since the opening of the Golden 1 Center in 2016 New residential and hospitality projects are poised to transform Sacramento's urban core into a true live/work/play destination Bank of Marin Bancorp American Bankshares River Source: S&P Global, California Credit Union League, Bureau of Labor Statistics, Colliers International, and Greater Sacramento Economic Council. 5#6Pro Forma Profile Enhanced Northern California Branch Footprint Top 5 Markets of Operation Sorted by pro forma deposits Cloverdale 128 Geyserville Rocklin Eldorad 99 Pollock Pines Rose Placerville Woodland- North Highlands Citrus Folsom He Eas 113 Heights Ra 50 irg County # of Branches(1) Deposits Market ($mm) Rank Angwin Windsor Sac Davist Florin 1 Marin San Dixon 10 $1,816 3 Elk Grove Rohnert Park Vacaville 2 Sacramento 4 $437 12 Fairfield Galt San Andreas Lodi Murphys Point Reyes Nati Seashore Vallejo San Pablo Richmond Benicia Martinez Pittsburg Antioch Pleasant Hill Walnut Creek Berkeley Lafayette 3 Sonoma 7 $396 12 BMRC (21) Concord Oakley Brentwood Stockton BMRC HQ 4 Alameda 3 $287 19 00 Danville Manteca AMRB (10) San Fran San Ramon zes Tracy San Leandro Ripon Riv 580 Dublin ★ AMRB HQ 5 Napa 2 $223 8 Daly City South San Francisco Hayward Livermore Note: Deposits for Amador, Placer and San Francisco counties not listed. Financial Highlights as of 3/31/2021 ($ in millions) 3/31/21 3/31/21 BMRC AMRB (2) Pro Forma Total Assets $3,058.1 $916.1 $3,974.2 Total Loans (excl. PPP) $1,756.8 $419.3 $2,176.1 Balance Sheet Total Deposits $2,656.2 $788.6 $3,444.8 Tangible Common Equity $316.5 $76.6 $393.1 2020 Net Income $30.2 $7.1 $37.3 Income Statement 2021E Net Income (3) $29.6 $8.4 $38.0 Market Cap Pre-Deal Market Capitalization $520.5 $97.5 $618.0 American River Bankshares (1) Bank of Marin Bancorp (2) Excludes purchase accounting adjustments. (3) Based on the sum of Q1 2021 reported earnings and Q2 2021 through Q4 2021 quarterly consensus estimates per FactSet. Source: S&P Global and FDIC Summary of Deposits. Deposit market data as of 6/30/2020. Market data as of 4/16/2021. Includes full service branches only. 6#7Transaction Assumptions Earnings Consensus earnings estimates for both companies • ~$6.1 million, or 35.0% of AMRB's standalone noninterest expense base Cost Savings • 25% phase-in during 2021, 90% phase-in during 2022, and 100% thereafter Transaction Expenses $9.5 million after-tax or 7.1% of aggregate deal value • Total gross credit mark of $6.6 million, or 1.56% of AMRB's loan portfolio (excl. PPP) Fair Market Value Adjustments - $0.3 million, or 4.7% of total gross credit mark associated with purchase credit deteriorated ("PCD") loans, recorded into ACL (5.00% of estimated PCD loans) - $6.3 million, or 95.3% of gross loan credit mark associated with non-PCD loans, recorded as a discount to loan value; amortized into earnings over 4 years (1.52% of non-PCD loans) Provision expense of $6.3 million to be taken immediately after close, included in pro forma tangible book value Positive loan interest rate mark of $5.2 million or 1.25% of AMRB's loan portfolio (excl. PPP); amortized from earnings straight-line over 4 years • AOCI netted for fair market value reduction of $1.5 million pretax; amortized into earnings straight line over 4 years Fixed asset write-up $1.3 million on AMRB's Healdsburg branch; 50% depreciated straight-line over 25 years Core Deposit Intangibles Bank of Marin Bancorp American River Bankshares • ~$3.4 million, or 0.50% of AMRB's non-time deposits Amortized sum-of-the-year digits over 10 years 7#8Transaction Overview Transaction Overview Fixed Exchange Ratio Consideration Mix Pro Forma Ownership Board of Directors Due Diligence Required Approvals Expected Closing Transaction Valuation 0.575 BMRC shares issued for each AMRB common share outstanding 100% Stock • 79.5% BMRC | 20.5% AMRB • 2 AMRB Board members to join BMRC Board of Directors Completed, including extensive loan and compliance review BMRC and AMRB shareholder approvals, and other customary regulatory approvals Q3 2021 Transaction Metrics Transaction Value(1)(2) $134.5 million 2022 EPS Accretion 12.9% Per Share Purchase Price(1) $22.46 2022 EPS Accretion (fully phased in cost savings) 14.2% Price / Tangible Book Value 1.75x TBV Dilution | Earnback 3.9% | 3.5 yrs Price / LTM Earnings(3) 15.9x Internal Rate of Return >15% Price/ 2022 Earnings 17.1x TCE / TA Ratio 10.8% 7.9% Total Capital Ratio 17.3% American River (1) Bankshares (2) Based on BMRC's stock price of $39.06 as of 4/16/2021. Includes consideration paid for AMRB shares and the value of AMRB options paid out in cash by BMRC. (3) For the period ended 3/31/2021. (4) Core deposits equal to total deposits less time deposits greater than $100,000. Core Deposit Premium(4) Bank of Marin Bancorp 00#9Bank of Marin Bancorp American River Bankshares Appendix#10Pro Forma Loan and Deposit Composition Bank of Marin Bancorp OO CRE 14% Res. RE 8% NOO CRE 40% American River Bankshares OO CRE 18% Multifamily 6% Farm + Agri. Res. RE 7% 1% C&I 17% C&D 4% Consumer & Other 10% Gross Loans (excl. PPP): $1,796,972 Yield on Loans: 3.96% DDA 54% Jumbo Time 1% Retail Time 3% Jumbo Time 6% Retail Time 4% MMDA & Sav. 41% NOO CRE 35% Pro Forma OO CRE 15% Multifamily 10% Res. RE 7% Farm + Agri. 1% C&I 17% C&D 4% Consumer & Other 8% Gross Loans (excl. PPP): $422,901 Yield on Loans: 4.76% DDA 44% NOW & Other 0.6% MMDA & Sav. 45% Total Deposits: $744,425 Cost of Deposits: 0.11% Loans / Deposits (excl. PPP): 56.8% Total Deposits: $2,509,670 Cost of Deposits: 0.07% Loans/Deposits (excl. PPP): 71.6% American River Bankshares Source: S&P Global. Financial data as of 12/31/2020. Note: Pro forma excludes purchase accounting adjustments. Bank of Marin Bancorp NOO CRE 39% Multifamily 7% Farm + Agri. 1% Consumer C&I 17% C&D 4% & Other 10% Gross Loans (excl. PPP): $2,219,873 Yield on Loans: 4.11% NOW & Other 1% Jumbo Time 2% Retail Time 3% 0 DDA 52% NOW & Other 1% MMDA & Sav. 42% Total Deposits: $3,254,095 Cost of Deposits: 0.08% Loans / Deposits (excl. PPP): 68.2% 10#11Contact Us Russell A. Colombo President & Chief Executive Officer (415) 763-4521 [email protected] Tani Girton EVP, Chief Financial Officer (415) 884-7781 [email protected] Tim Myers EVP, Chief Operating Officer (415) 763-4970 [email protected] Media Requests: Beth Drummey VP, Marketing & Corporate Communications (415) 328-3063 [email protected] Bank of Marin Bancorp American River Bankshares 11