1
                                   EXHIBIT 99

UNITED SECURITY BANCORPORATION TO ACQUIRE GRANT NATIONAL BANK; BANK HAS TWO
BRANCHES WITH $32 MILLION IN ASSETS IN CENTRAL WASHINGTON.

         Spokane WA - March 24, 1998 - United Security Bancorporation (NASDAQ:
USBN) today announced it has reached a definitive agreement to acquire Grant
National Bank, which is headquartered in Ephrata, Washington and has a second
branch in Moses Lake, WA. Grant National will retain its own name, staff and
Board of Directors. It will join the Bancorporation's existing family of
community banks - United Security Bank, Home Security Bank, and Bank of Pullman
- - as its fourth independent banking subsidiary. With the Grant acquisition, USBN
will have a total of 26 community bank branches.

         Based on yesterday's closing price of United Security Bancorporation,
Grant National Bank shareholders will receive approximately 14 shares of United
Security Bancorporation common stock for each share of Grant National they
currently own. Total consideration paid will be approximately $10 million - or
about 2.9 times Grant's 1997 year-end book value. The 33,000 shares of Grant
National are primarily owned by residents of Grant County and do not trade on an
exchange. The transaction, which has been approved by the boards of directors of
each company, is expected to be completed in the third quarter of 1998 subject
to approval by Grant National shareholders and regulatory agencies. It will be
treated as a pooling of interests for accounting purposes.

         Grant National Bank had approximately $33 million in total assets, $30
million deposits, and $21 million in loans at December 31, 1997. United Security
Bancorporation had total assets of $350.5 million, total deposits of $307.6
million, and loans of $226.7 million at year end.

         "Using conservative growth assumptions, and factoring in minimal
provision for operating cost savings, we expect this acquisition of Grant
National to be accretive to earnings during 1999 and cause only minor dilution
to earnings in the first year," noted Chairman and Chief Executive Officer,
William C. Dashiell. "Ephrata is the county seat of Grant County and has a
stable business and farm economy. Moses Lake is, among other things, site of one
of the longest airport runways in the US and we believe the area has excellent
potential." Both Grant National and United Security focus on small business
banking and superb customer service.

         "USBN's 1997 acquisition of five branches from Wells Fargo (NYSE: WFC)
included a small office in Moses Lake. We will be studying customers' banking
preferences and involve them in our ultimate decision regarding consolidation of
our staffs. We intend to provide our market area and employees the best possible
opportunities. And, we will continue to evaluate additional, appropriate
partners to join the USBN banking family," Dashiell said.

         "Grant National is a logical expansion of our presence in central
Washington. Larry Mitson, Grant's president, and his excellent staff have
extensive experience and will play an integral part in helping grow our
franchise in this region," said Richard C. Emery, President and Chief Operating
Officer. "Larry and I started out as bank trainees together at Old National Bank
in 1963 and we have been close personal and professional friends for years.
Larry is widely known for his successes at Old National and Farmers & Merchants
Banks in Spokane, at 


                                        1
   2
Community State Bank in Blaine, and at Ben Franklin Bank in Pasco. We are
excited about bringing him and his team under the United Security Bancorporation
banner."

         "Personally, I'm very pleased to be joining United Security," Mitson
said. "I have enormous respect for the team of Bud Dashiell and Rich Emery's
banking talents and have been impressed by United Security's growth over the
past several years. Our two organizations will form a very effective combination
that is dedicated to customer service, community businesses, customer banking
and community involvement. I am confident our employees and customers will be
right at home in joining USBN."

         Founded in 1989, nationally-chartered Grant National had total equity
of $3.4 million at December 31, 1997. Grant's return on average assets was 1.4%
and its return on average equity was 13.5% for 1997.

         United Security Bancorporation is a multi-bank holding company. Its
three banking subsidiaries include United Security (based in Spokane), Home
Security (based in the Yakima Valley) and Bank of Pullman (based in Pullman,
near the Idaho border). USBN has 24 branch offices - 23 in Central and Eastern
Washington and one in Idaho. In addition, the company owns USB Insurance, a
full-line insurance agency, USB Mortgage, a mortgage company, and USB Leasing, a
commercial leasing company. USBN closed at $20.75 in trading on the NASDAQ
national Market System yesterday, March 23.

Safe Harbor Statement under the Private Securities Litigation Reform Act of
1995: Statements in this news release looking forward in time involve risks and
uncertainties, including regulatory approval, completion of the due diligence
process, success of acquiring new locations and integrating newly-acquired
branches, additional expansion opportunities, the effect of changing economic
conditions, product demand, changes in the regulatory environment, and other
risk factors detailed in the company's Securities and Exchange Commission
filings.


                                       2