The Blue Hill Meteorological Observatory in Milton, Massachusetts is the foremost structure associated with the history of weather observations in the United States.

Knowledge of wind velocities, air temperature and relative humidity at various levels came into use as vital elements in weather prediction due to techniques developed at this site.

On August 4, 1894 the first atmospheric sounding in the world was accomplished at the observatory, with a weather kite carrying a thermograph 2,030 feet above sea level.

[6] The observatory remains active to this day, continuing to add to its database of weather observations now more than one hundred years old, and stands as a monument to the science of meteorology in the United States.

Rotch chose the site because the elevation of 635 feet was the highest point within ten miles of the Atlantic Ocean, on the East Coast south of central Maine.

The original structure consisted of a two-story circular tower and an adjoining housing unit which contained two bedrooms, a dining room and a kitchen.

Native stone, gathered from the summit of the Great Blue Hill, was used for the two-story tower, adjoining housing unit, and the east and west wings.

The concrete construction of the tower was chosen specifically to provide the maximum amount of stability and durability in the event of high winds.

In 1962, a metal tower containing a siderostat for collecting the sun's rays and directing them by mirrors to an optical bench inside the observatory, was erected adjacent to the west wing for studies related to the upper atmosphere.

In 1980, the building was listed in the National Register of Historic Places as "Great Blue Hill Weather Observatory", as part of a multiple property nomination by the Commonwealth of Massachusetts entitled "Prehistoric and Historic Resources of the Blue Hills and Neponset River Reservations and Selected Adjacent Lands".

A white marble stone containing a summary record of climatological data from 1885 to 1984 and dedicated to the memory of Abbott Lawrence Rotch is located on the front yard of the building.

For this reason, the National Oceanic and Atmospheric Administration designated the Blue Hill Observatory one of 26 International Benchmark stations within the United States.

During the 1950s, the site housed a research group that used radar to scan approaching thunder storms as far away as western New York State, as part of an inquiry into the causes of lightning.

The installation consisted of a steel tower supporting a second-hand military radar set, several Quonset huts and box trailers, surrounded by a chain-link fence.

This era coincided with the end of the long career of the famous Director of the Observatory, Dr. Charles Brooks, said to be one of the few who accurately forecast the path of the destructive Hurricane of September, 1938.