Also known as the Blue Hill Observatory, the Blue Hill Meteorological Observatory is home to the oldest weather data base in North America and is the oldest, continuously operated observatory in the United States. The observatory was built in 1884 on top of Great Blue Hill in Milton, Massachusetts. Despite the seemingly never-ending difficulties the observatory was experiencing during the first year of its operation, Abbott Lawrence Rotch (a meteorologist who founded and built the observatory) was unstoppable in pursuing his interest in the weather.

Considered to be a monument to the science of meteorology in the United States, the observatory stands on the highest point within ten miles of the Atlantic Ocean, a perfect location that gave for a unique opportunity for observing and studying weather behaviors. Originally built as a private weather station and research facility, the Blue Hill Observatory quickly became famous for its pioneering studies of the upper atmosphere and is now the main source of atmospheric observations including climatology of cloud type, velocities, heights and directions as well as worldwide soundings of pressure, temperature, humidity and sometimes wind speed dating from more than one hundred years ago.

When the observatory opened, Rotch and his group were using a few gauges and equipment to observe the sky but in 1894 a New York journalist William Eddy introduced and demonstrated how his kites could elevate instruments. Soon after, Malay kites made by Eddy holding light-weight thermograph were securely hovering above the surrounding of the observatory. Although extremely strenuous, especially when breakaways occurred and a lengthy brass piano wire used to fly the kites had to be retrieved, the use of kites lifting the equipment needed to record information up in the sky was undoubtedly beneficial. With the changing times, developments had to be introduced and the observatory has to adapt to it, thus, between 1935 and 1936 the use of balloons was implemented. This improvement brought about the first successful radio-meteorograph flight and poineered the development of the radiosonde in the United States.

The simple-looking building of the observatory was constructed originally with a two-story circular tower adjoined by a two-bedroom housing unit complete with a dining room and a kitchen. With the need for more space, an additional two-story structure was built on its west wing. In 1908, the original tower was replaced by a fortified three-story concrete tower that was made of Gothic Revival style. In 1962, a metal tower was erected to hold a siderostat used for collecting the sun's rays and directing them by mirrors to an optical bench inside the observatory. Although built weather proof, the observatory had to undergo several renovations to maintain its operation making it now both an International Benchmark Climate Station and a National Historic Landmark.