The Oldest National Monuments In The United States

(via 99 Percent Invisible)  The Residence Act of 1790 called for the creation of a new capital city for the United States. Dividing up land previously belonging to Maryland and Virginia, a diamond spanning ten miles on each side was marked at each mile with a similar stone. And while a majority of these 40 markers still exist today, their conditions vary and each one has come to tell its own unique story over the centuries.