UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 10-Q (Mark One) ☑ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended September 30, 2019 or ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15 (d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from __________ to __________. Commission file number: 001-09383 WESTAMERICA BANCORPORATION (Exact Name of Registrant as Specified in Its Charter) California ...

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 10-Q (Mark One) ☑ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended June 30, 2019 or ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15 (d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from __________ to __________. Commission file number: 001-09383 WESTAMERICA BANCORPORATION (Exact Name of Registrant as Specified in Its Charter) California 94-21 ...

Title of Class Shares outstanding as of April 30, 2019 Common Stock, 26,929,915 No Par Value Securities registered pursuant to Section 12(b) of the Exchange Act: Title of each class Trading Symbol(s) Name of each exchange on which registered Indicate by check mark whether the registrant is a shell company (as defined in Rule 12b-2 of the Exchange Act). Large accelerated filer ☒ Accelerated filer ☐ Non-accelerated filer ☐ reporting company," and "emerging growth company" in Rule 12b-2 of the Exchange Act. (C ...

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 10-K (Mark one) ☒ ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the fiscal year ended December 31, 2018 or ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from ______________ to______________. Commission File Number: 001-09383 WESTAMERICA BANCORPORATION (Exact name of the registrant as specified in its charter) CALIFORNIA ...