Just off of Astor Point within the confines of Copper Harbor you’ll find this unique marker carved into the rocky shore. It marks the specific latitude of 47º 28′ 11″ as it makes its way through the Keweenaw, but also seems to mark the location of the nearby Copper Harbor lighthouse which sits directly across the harbor at Hays Point. In fact just inland from this marker stands the harbor’s front range light, followed by the old rear light and residence back by the highway. These two coincidental occurrences always made me feel that this particular marker had something to do with the Lighthouse Service, a theory which seemed to be further strengthened by the U.S.L.S. etched under the coordinates. Turns out I was a little off, by a good 5o years.

A closer look at the etching reveals a date – 1864. Considering the United States Lighthouse Service didn’t exist until 1910 (an agency that was previously known up until then as the Lighthouse Board), it became clear that the U.S.L.S. etched into the rock stood for something else. Turns out it actually stood for the United States Lake Survey, a hydrological survey appropriated by congress in 1841 to map the Great Lakes. The survey was based in Detroit and took 41 years to complete (!), finally ending in 1882. In the end the survey produced over 70 nautical charts of the lakes and their related collection of harbors, bays, and tributaries. Apparently this etching was done in accordance to that survey, though why this particular latitude was important enough to mark is beyond me. My guess is still on the lighthouse though….