Our offices are closed today to honor Dr. Martin Luther King, Jr.. If you are visiting the @NationalMallNPS you can learn about the geology of many of the building stones of our nation's capitol here: https://t.co/qcRgRXVVHc https://t.co/8iO0IGgTVa
RT @USGS_Pubs: This #PresidentsDay learn about the stones used to build the buildings of our Nation's Capital https://t.co/663ywUXNqa https…
RT @USGS_Pubs: This #PresidentsDay learn about the stones used to build the buildings of our Nation's Capital https://t.co/663ywUXNqa https…
This #PresidentsDay learn about the stones used to build the buildings of our Nation's Capital https://t.co/663ywUXNqa https://t.co/hCCFG4Sfiv