Travelers often stopped for the night at Jenk's Tavern in Spencer, as did General Henry Knox, pushing his cannons through the streets of the town on his way to Boston from Ticonderoga, and George Washington in 1789.

When the War of Independence broke out in 1775 it found Spencer ready to take part; fifty-six men under Captain Ebenezer Mason immediately set out to Boston.

A total of 313 Spencer men are known to have served in the Civil War; thirty-two lost their lives in the service of their country.

His business flourished in his family until 1916, when it merged with Wickwire Steel Co. At one time, Spencer had 11 factories and 26 buildings for wire drawing.

In 1888–1889, four prominent citizens (David Prouty, Richard Sugden, Luther Hill and Nathaniel Myrick) presented the town with a new high school, a library, a public park and the Spencer Agricultural Fair Grounds.

Spencer is home to Saint Joseph's Abbey, a cloistered Roman Catholic monastery of monks of the Cistercian Order of the Strict Observance, popularly known as Trappists.

The official cause was a malfunction of the system due to operator error, that regulates the amount of lye released.

According to local news reports, dozens of people received medical treatment for "burning sensations and skin rashes".

Spencer has many acres of preserved parks and hiking areas, such as the Burncoat Pond Wildlife Sanctuary, which is protected by the Massachusetts Audubon Society, and Spencer State Forest/Howe State Park, marking the birthplace of inventor Elias Howe.

On November 18, 2015, more than 200 students from David Prouty High School took part in a sit-in in protest of the district's administration.

Protesting the lack of current textbooks, cuts in the music and theater programs, the band, and the Student Council, they walked out of class and spent the day in the gymnasium.

Having not been satisfied with having their voices heard at the School Committee meeting the night before, they were targeting the superintendent, Tracey Crowe, whom the district's teachers had also given a vote of no confidence in.