The bank earned a reputation for aggressive business practices and benefited from economic and population growth in the Western United States.

By the mid-20th century it had an international presence, and was ranked the fifth-largest bank in the United States and third-largest in California in terms of deposits.

In 1978, computer consultant Stanley Rifkin learned the electronic codes Security Pacific used to telegraph funds to other banks.

They were among the most heavily armed bank robbers in history, carrying semi-automatic firearms, handguns, and improvised explosive devices, and succeeded not only in stopping several patrol cars but forcing a San Bernardino police helicopter to give up pursuit.

By the end of the Norco shootout, a police officer and two robbers had been killed, with the other three suspects arrested and sentenced to life in prison.

The agreement stipulated that the management of Bank of Canton would remain in place and that Russell Fok would continue as chairman of the board.

Earlier, BoC had revealed plans for a major expansion in the United States, concentrating on the growing Asian community in California.

SPNB finally acquired American Asian Bank, controlled by individuals associated with the ailing Hong Kong–based Tung Group.

The 1980s boom for a time sustained the bank, but its aggressive acquisition strategy, unfavorable financial engineering arrangements, and the 1990 recession and Southern California real estate crash devastated its loan portfolio and balance sheet.