Goodsell Observatory is a building on the campus of Carleton College in Northfield, Minnesota. It was constructed in 1887 and was, at the time, the largest observatory in the state of Minnesota. It was named for Charles Goodsell, who donated much of the land on which Carleton was founded. Goodsell was built to replace Carleton's original observatory (built in 1877), which was razed in 1905 to make room for Laird Hall. Goodsell Observatory is on the National Register of Historic Places.
The observatory's first central telescope, purchased in 1877, was a 8 1/4" refractor manufactured by Alvan Clark and Sons. In 1890, the college acquired a 16.2" refractor produced by the famous John Brashear of Pennsylvania. It was then the twelfth largest refractor in the world and sixth largest in the United States. In 1922, Carleton professor Edward Fath constructed one of the nation's first photoelectric photometers in Goodsell.
From the late 19th century to the end of the World War II, Goodsell kept the time for every major railroad west of the Mississippi, including Northern Pacific Railway, the Great Northern Railway, the Chicago, Milwaukee, and St. Paul Railroad, and the St. Paul, Minneapolis, and Manitoba railroads.
A US Signal Corps station was placed at the observatory in 1881 and transmitted meteorological data to Washington. Goodsell also served as the headquarters of a state weather service from 1883 to 1886.