Putnam was incorporated in 1855, which separated it from Killingly, Pomfret and Thompson. The town was named in honor of Revolutionary War General Israel Putnam.
Putnam was a key contributor in providing clothing and other goods to the Civil War soldiers. There were numerous mills and a train ran through the town, providing transportation for the goods being produced.
On Aug. 19, 1955, Putnam was devastated by floods resulting from torrential downpours caused by two hurricanes, which hit Connecticut within the span of a week. Hurricane Connie affected Connecticut on Aug. 13, dropping between four and six inches of rain across the state. Hurricane Diane soaked the state with 14 inches of rain on Aug. 18-19. The result was flooding in many of the state's rivers, including the Quinebaug River. The resulting torrent of water destroyed homes, businesses and factories. Floating magnesium barrels burst, lighting up the night. The railroad bed was washed away.
