Description:Principal Ports are defined by port limits or US Army Corps of Engineers (USACE) projects and exclude non-USACE projects not authorized for publication. The determination for the published Principal Ports is based upon the total tonnage for the port for the particular year; therefore the top 150 list can vary from year to year. The Principal Port file contains USACE port codes, names, and commodity tonnage summaries (total tons, domestic, foreign, imports and exports). All units for the values are in tons. (NOAA, 2017)