🔭 Calais Observatory

The Calais Observatory is a pair of granite fixtures in Meridian Park in Calais, Maine. The two stones were used for mounting scientific equipment used in a variety of astronomical observations, principally for the accurate calculation by the United States Coast Survey of Calais's longitude with respect to meridians in Cambridge, Massachusetts, and Greenwich, England. The site was listed on the National Register of Historic Places in 2012, and is part of the National Oceanic and Atmospheric Administration's Heritage Trail program. At the time of its longitude determination in 1866 with respect to the Greenwich Meridian, it was arguably one of the most precisely located places in the United States.