Before Lancaster had a public library, it had several private subscription libraries. The two that served as predecessors to the public library were the Social Library and the Library Club.

The Social Library, also sometimes referred to as the “Lancaster Library,” was founded in 1790 and operated for 60 years. The Social Library dissolved in 1850, around the time that Clinton separated from Lancaster, and the collection was sold off to its members.

The Library Club was founded in 1851, shortly after the Social Library dissolved. It too was a subscription library, and members paid $3 in annual dues.

Many of the members of the Library Club had also been members of the Social Library. Many members were also prominent citizens in town, including the Reverend George M. Bartol and Mary Ann Thayer.

Around this time there were also several other Libraries in town, including an Agricultural Library, a Sabbath School Library, and several School District Libraries, all indicating that Lancaster had a very strong interest in reading and learning even in the mid-19th century.

In 1862 the Library Club decided to offer the town their collection on the condition that the town increase taxes to accommodate and support a public library.

The Library’s collection in 1862 included over 600 volumes from the Library Club, and over 200 books from other libraries in town, including the Agricultural Library, School District Libraries, and the Sabbath School Library.

The Library was initially located in the Town House, which was located in the middle of what is today the Town Green, on the second floor of the building. A year later, in 1863, the Town Museum was established, and housed in the Library.

Shortly after the end of the Civil War, the Town began making plans to build a monument to those from Lancaster who had given their lives during the War. Coincidentally, the Town also needed a new home for its growing Library collection, and Memorial Hall was built to serve as a Civil War Memorial Library.

The total cost of the building was $30,000, $20,000 of which was donated by Nathaniel Thayer Jr., one of the wealthiest men in New England and a native Lancastrian.

Memorial Hall was expanded in 1888 due to needing more space to house the Library’s growing collections. As during initial construction, the Thayer family led the way with financial assistance. The project was funded by Nathaniel Thayer Jr.’s four sons: Nathaniel III, Eugene, John Eliot, and Bayard, in memory of their father, Nathaniel Thayer Jr., who had passed away in 1883.

The expansion included adding additional rooms, more space at the back of the building for book stacks, and changing the building’s facade.

A cupola was also added above the skylight, but was removed before 1900 due to roof problems.

The next addition to the Library did not come until 1929, when the Children’s Room was built. The Funds for the addition came from Mrs. Bayard Thayer, who donated the funds for the room in memory of her son, Nathaniel Thayer II, who had died in 1927.

The Children’s Room was one of the first dedicated spaces for children in a public library in the Commonwealth of Massachusetts.

In 1996, the Lancaster Public Library received a grant from the MBLC for the expansion and renovation of the building. The expansion added the Reference Room, more than doubling the building’s square footage. Other additions included a modernized and enlarged Special Collections room, two meeting spaces, and new stacks at the back of the building with enough space to hold over 70,000 volumes.

When the Library reopened in 1999, the Board of Trustees rededicated the newly renovated Library as the Thayer Memorial Library in recognition of the contributions made by the Thayer family throughout the Library’s history.