With this article we use an alternative form of the discrete choice model to analyze the distribution of maritime shipments among US ports. We model the distribution as a function of the characteristics that describe each shipment and each port. We assume that vessel schedules are fixed in the short-term and examine the assignment to ports for exports of various commodity-types as a function of geographic location, port characteristics, and characteristics of vessel schedules. We find that the most significant characteristic of a port is its location. We show also how the market share predicted for a port can be expected to vary with each commodity-type and each carrier, and we show how the choice process varies for discretionary cargo.