In 1872, a team of astronomers from Brazil began planning an expedition to Saint Thomas to observe the upcoming 1882 transit of Venus, when the planet would pass in front of the Sun.

The observatory spot was chosen on a hill on the Estate Mafolie due to its elevation, rising above the city of Charlotte Amalie and allowing an uninterrupted view of the sky.

Astronomers that took part in the expedition included Antonio Luis von Hoonholtz, Francisco Calhejros da Graca, and Arthur Indio do Brasil.

The marble tablet that was used as an instrument station during the transit is now used as a plaque, written in Portuguese.

[2] For its notability and contribution to the field of astronomy, the site was listed on the National Register of Historic Places in 1978.