Statement of Significance (as of designation - February 17, 2006):
The Portland Observatory is the only known surviving example of a maritime signaling station. Maritime signaling stations were once prominent fixtures along the coast and in important port towns relaying messages from ship to shore. Visual communication between ship and shore meant that merchants and ship owners could both receive and send messages to their vessels several hours before the vessel reached port. Consequently, owners could learn of problems the vessel might have encountered on its travel such as damaged cargo. This method of communication also enabled a ship owner to redirect his vessel to another port if the cargo had been sold or to reserve a berth on the wharves and hire a crew of stevedores to unload and reload the vessel in a timely fashion.