Killingly was inhabited by Native Americans for thousands of years. They called the East Killingly area “Chemaug.” One of their trails, which followed sections of Route 101 and Bear Hill Road became a major colonial path between Providence and Hartford.

In 1711, a 1600-acre tract of land was bought from John Chandler of Woodstock which was known as the Chestnut Hill Purchase. It was located on the beautiful hill that at that time was covered with stately chestnut trees. Although the village is now known as East Killingly, its early name has never been forgotten and is inseparable from its history.

The Industrial Revolution of the early nineteenth century changed the focus of the region from one of primarily farms to a beehive of activity as mill after mill was constructed along the mighty stream known as the Whetstone Brook. The brook originates in the Old Killingly pond, a spring-fed body of water. In its first two hundred yards, the Whetstone makes a very rapid descent of more than seventy feet. This fall is capable of generating an estimated 400 horsepower which made it one of the prime sites on the stream. In all, this stream drops almost 200 feet before it joins the Five Mile River at Elmville.

The area around the Whetstone Brook takes its name from the fact that it was well known among Native American tribes as a source of materials for projectile points. The stream’s first industrial utilizations were sawmills and grain mills dating from about 1715. Some of the mills along the Whetstone were: Chestnut Hill Mill that later became Acme Cotton Products Co., Inc., The Whitestone Co., Judge Young’s Mill, Leffingwell Mill, Davis & Brown Woolen Co. (later sold to Hale Mfg. Co.), Greenslitt Mill, Elliotville Mill, and Peeptoad Mill. Some of the mills were built of stone from a nearby quarry.

The picturesque Peeptoad Mill and the double stone-arch bridge are listed on the National Register of Historic Places.

Some early photographs of the area of East Killingly known as The Valley identified it as Pleasant Valley. A portion of the North Road and vicinity are called Tucker District and Kentuck Woods.

Beginning in the mid 1800s the village was bustling. There were several general stores, a post office, two churches, a school, and a blacksmith shop.

Although the railroad bypassed East Killingly, the electric street railway provided both passenger and freight service to Providence from 1902 until 1920. The right-of-way was south of Whetstone Brook, which it paralleled all the way to its terminus in Elmville where it connected with the Shore Line route to Alexander’s Lake, Webster and Worcester, Massachusetts. A substation in Rhode Island powered the line. Building the electric railway lines required a work force of about 100 men and very little in the way of machinery.

Through the years there were three churches to serve the religious life of the community: the Union Baptist Church organized in 1776, the Free Will Baptist Church, and Our Lady of Peace Catholic Church built in 1944-46.