In 1955, eighteen women founded the Haddam Historical Society to preserve the rich and diverse history of Haddam. The early mission called for the Society “to preserve whatever may relate to the civil, military, literary, ecclesiastical history of the town; to investigate such traditions as now exist only in the memory of aged persons; to maintain collections of books, newspapers, maps, art, manuscripts, furniture, archaeology, natural history, curiosities and antiquities of every kind as may illustrate the local history of the Town and to encourage historical and antiquarian investigation and disseminate historical information.”

The early constitution also called for the Society “to instill in our fellow citizens an understanding of the past, knowledge and pride in our heritage; the preservation of records and monuments still remaining and to promote and encourage civic undertakings to that end.” During the first decade, members met in private homes and local public buildings. Early activities focused on local history programs and community outreach. The organization was one of the area groups who worked to save the Goodspeed Opera House and protect historic homes and sites during the construction of Route 9.

In 1962 Haddam celebrated its Tercentenary and the Historical Society played a leading role in the commemoration. The Society produced an exhibition covering 300 years of Haddam history and invited honored guests from around the world to attend festivities. One of the honored guests was Mr. Isaac Arnold of Houston, Texas, a great-great grandson of Thankful and Joseph Arnold. He toured the family’s historic homestead in the center of Haddam Village and purchased it with intent of providing the Haddam Historical Society with a permanent home.

After two years of painstaking restoration work, the Thankful Arnold House was dedicated on May 29, 1965 as a community museum and headquarters of the Society. The property was leased to the organization for $1.00 a year until the death of Mr. Arnold in 1973 at which time it was transferred to Society. The house was restored to its circa 1794-1810 appearance and opened for tours. The house has recently been reinterpreted as the home of Widow Thankful Arnold during the 1820s. For a complete tour of the house please refer to the section on the Thankful Arnold House.

In 1973 the Wilhelmina Ann Arnold Barnhart Garden was dedicated and since then has been awarded a Connecticut League of Historical Societies Award of Merit. Today the garden displays herbs and vegetables Thankful Arnold would have used c. 1825.

Since the early 1970s, the Society has been the sponsor of the Connecticut Spring Antiques Show, one of the country’s most important venues for authentic early American furniture and accessories. In 1987 the Society purchased the rights of the show and it continues to be the organization's largest fundraiser.

The Society assisted with the State Historic Resource Inventory conducted by the Greater Middletown Preservation Trust in the early 1980s and provided material for the publication “Portrait of A River Town.” The Society also sponsored the Haddam Center Historic District, which was listed to the National Register of Historic Places in 1988.

In the last decade, the Society has conducted an architectural and conservation assessment of the Thankful Arnold House and its contents, a study of the genealogy of the Arnold Family and a new interpretation of the museum and its collections. The Society has also expanded education programs, and reinterpreted the herb garden. We are now a proud member of Connecticut’s Historic Gardens.

Today, the Society continues to offer programs, tours and lectures on local history. Recently the Society has conducted tours of Haddam’s Historic Churches, industrial sites along Candlewood Hill and a Connecticut River Boat Tour. Local history programs have included Haddam's Historic Railroad Stations, the CCC at Camp Filley in Cockaponset State Forest, the shards found in the Thankful Arnold House, Higganum Reservoir Dam and the Shailer and Knowles Factory in Shailerville. The Society also sponsors programs on variety of historical subjects and recent topics have included Wallace Nutting, daguerreotypes, and Theorum painting to name a few. Hands-on workshops are also a popular activity and the Society has demonstrated how to dip candles, make clothespin dolls and felting.

The Society continues to expand its collection of artifacts related to the history of Haddam and the Arnold Family and acquire period appropriate items to display in the house. Over the years the collections have been carefully documented, catalogued and stored and are available for use by researchers, historians and interested parties.

The Society has installed small exhibits around town, in the Library, Town Hall and local businesses, which have featured such subjects as Granite Rock Springs/Undina Beverage Company, Higganum’s Industrial Past, Historic Schoolhouses in Haddam and Haddam during the Civil War.