Without doubt, Portland's largest ghost sign (almost a football field in overall length), and in my opinion, the most unique.
In 2002 a 120,000 square-foot wood, steel and concrete dock on the river was demolished to prepare for construction of the Riverscape condominium project. That demolition uncovered this great "IBD" painted on the old existing seawall. The bottom photo shows Terminal 1 after the concrete had been removed, exposing the steel girders. Under the steel is the original seawall with the lettering.
Barney Blalock, webmaster of the very informative Portland Waterfront website, thinks this may have stood for "International Breakbulk Dock." Break bulk cargo refers to loose material un/loaded individually, as opposed to today's container carriers or bulk materials like grain or oil.
I discovered this ghost sign while coming downriver on the navy's USS Kidd (DDG-100) in June. You can see it from the river, or from across the river on N. River Street where I took the top photo.
(2002 Photo: DemolitionX)