also List of astronomical observatories List of National Historic Landmarks in Maryland National Register of Historic Places listings in Montgomery County, Maryland References External links City web site about the observatory 1989 Drawings of the Gaithersburg Latitude Observatory at the Library of Congress , including photo in 1991, at Maryland Historical Trust National Historic Landmarks in Maryland Government buildings on the National Register of Historic Places in Maryland Government buildings completed in 1899 Historic districts on the National Register of Historic Places in Maryland Astronomical observatories in Maryland Buildings and structures in Gaithersburg, Maryland Historic American Engineering Record in Maryland 1899 establishments in Maryland National Register of Historic Places in Montgomery County, Maryland