[click image to enlarge]
This U.S. Geodetic Benchmark is located on the property of a famous Quincy landmark in the Historic District of Quincy Center. All across the continental U.S. as well as in Alaska and Hawaii there is a network of survey monuments which are bronze disks like the one pictured here about 8 to 10 cm. in diameter set in rock or permanent structures. The exact number can only be guessed at, but they have been placed in all kinds of locations from city sidewalks and bridges to remote ridges and mountain tops. These have been set by surveyors beginning in 1879 and are the basis for horizontal and vertical control (measuring elevation) for all the physical mapping done in the US.
Come back tomorrow and Wednesday and I'll show you more of the Quincy landmark where I found this Benchmark. Have you spotted any "benchmarks" where you live?