During World War II, the Royal Canadian Navy wanted to understand more about the propagation of radio waves and how they were affected by the earth’s ionosphere in order that German radio transmissions could be intercepted in a more efficient manner. In co-operation with the National Research Council, the RCN established a “field intensity station” at Chelsea in 1941 to monitor the height of the ionosphere
Chelsea, also known as an ionospheric observatory, was established in 1941 and closed down in 1947. It was located on the north side of Old Chelsea Road a few hundred yards west of Highway 105. The Chelsea station operated during the post war period but in 1947, its work was transferred to the Defence Research Board’s new Radio Propagation Laboratory in Ottawa. Shortly thereafter, the station was demolished. Today, there are no traces of the single shack or the many masts that were once erected on the property.
The municipality has a reputation for being environmentally responsible and was one of the first in Canada to ban the use of pesticides. While 60% of the area of the municipality consists of Gatineau Park, much of the rest of Chelsea is residential with mostly large lots, and tracts of undeveloped land. It has a distinctly rural feel. The population of Chelsea is almost evenly divided between anglophones and francophones and both English and French languages are in common use throughout the town.
A new sports complex, the Meredith Centre, was developed on the main road, neighboring the English Elementary School. The new complex hosts a hockey rink, community rooms, and soccer fields.
Chelsea is named after the New-Vermont town of its first settler, Thomas Brigham. The name has been in use since the early 19th century: Old Chelsea (1819), Parish Saint-Stephen-of-Chelsea (1835), Chelsea (circa 1870).
Part of the film Grey Owl was shot on the Gatineau River. A number of regionally and nationally well-known musicians, filmmakers and artists live in Chelsea, including Ian Tamblyn.