The land was first called Matherstown in honor of Samuel Mather Jr. who claimed ownership. Later, after William Hart's heirs won the legal dispute over ownership, it was named Hart's Grove and eventually this was changed to Hartsgrove.

The township was the last in the county to be settled. It wasn't until 1822 that the Alderman cousins from Windsor built the first dwellings in the area.

For many years, the area was the hunting grounds for Indians and settlers of neighboring townships. The land remained heavily timbered, well supplied with springs and streams of clear water and the forests were filled with wild animals.

For more than twenty years, while the lengthy battle in court continued, Hartsgrove remained a wilderness while adjoining localities began to show evidence of civilization.

The township land was inherited by Richard W Hart. When one of his daughters married the Rev. William Jarvis of Chatham, Connecticut, he deeded to them the northern half of the township, about 8,000 acres.

Judge Mills of Saybrook, Connecticut, was Mr. Hart's agent for the remaining land until Hart's death when half was given to Mrs. Jarvis and her sister, Hetty B. Hart in 1837 or 1838. William Jarvis II and Gen. Charles Stearns then became the agents until 1840 when Stearns was elected sheriff and moved to Jefferson. In 1878, Jarvis was still serving as agent.

George Alderman of Windsor was the first to come to Hartsgrove when he erected a log cabin in 1822. His cousin. Frederick Alderman, came the following year.