Old Naval Observatory

The Old Naval Observatory is a Greek Revival building with a central dome in Washington, D.C., originally designed for astronomical measurements and research. The complex housed specialized instruments and facilities dedicated to observing the sky and conducting scientific investigations.

The facility was established in 1844 and served as the first national observatory of the United States until 1893. During this period, it conducted fundamental astronomical measurements and maintained the nation's official time standard.

This facility played a crucial role in establishing America's scientific independence and helped standardize timekeeping across the nation. The work done here also influenced improvements in navigation methods for maritime use.

The complex is located along E Street NW in Washington and no longer operates as an active observatory today. Visitors should know that the building now houses administrative offices and access may be limited to certain areas or times.

An astronomer named Asaph Hall used the facility's 26-inch refracting telescope, which was the largest in the country at the time, to discover Mars' moons in 1877. This discovery stands as one of the most significant scientific achievements made at the site.

Location: Washington, D.C.

Inception: 1843

Official opening: 1843

GPS coordinates: 38.89500,-77.05194

Latest update: December 9, 2025 18:40