California is the largest economy among states in the US. More than 40% of the nation's containerized cargo flows through the marine ports of California. Cruise ships also call on four of California's largest ports, with the Port of San Diego growing the fastest. This study assessed the attack risk for the Port of San Diego by applying a model from the risk assessment framework recommended by the Department of Homeland Security. Quantification of the model's threat and consequence factors was based on economic data derived from various databases. The findings show that the risk of attack is more pronounced for cruise ship operations than for marine cargo operations. The risk is directly proportional to the level of vulnerability to expected perpetrator tactics and weapons. Based on expert knowledge of the port characteristics, the vulnerability assessment points to a low probability that anticipated attack methods could succeed. However, the behavior of terrorists can be unpredictable as they continuously adapt to exploit vulnerability gaps that may be unforeseen. Therefore, it is wise to develop policies that encourage a security culture to avoid complacency and to conduct regular risk assessments.