Williams College's Hopkins Observatory: the oldest extant observatory in the United States

The Hopkins Observatory, built at Williams College in 1836-1838, is the oldest astronomical observatory extant in the United States. Founded by Professor Albert Hopkins and built together with his students, it still contains the oldest known Alvan Clark telescope. Some of its historic instruments are mounted in its wings, known as the Mehlin Museum of Astronomy, and its central internal domed-ceiling room is the Milham Planetarium.