Portland Observatory
Portland, United States
<br><center>has been designated a<br> <b>National Historic Landmark</b><br> This site possesses national significance<br> in commemorating the history of the<br> United States of America.<br> The Observatory is the nation's only remaining maritime signal tower. It served as a communication station for Portland's bustling harbor brom 1807 to 1923, announcing the arrival of ships with a unique system of colorful signal flags.<br><br> <b>National Historic Civil Engineering Landmark</b><br> Built 1807</center><br> One of the earliest marine signal stations in the United States, this tower is unique in its engineering design and construction and contributed to the prosperity of Portland harbor as a vital center of maritime commerce during the "Golden Age of Sail"