The Thayer Memorial Library’s origins date to 1790 when its predecessor, the Lancaster Library (later renamed the Lancaster Social Library), was first established. Membership cost three dollars and required a two-thirds vote of the proprietors to join. In 1862 Lancaster residents first established a tax-supported, free public library—the Lancaster Town Library. Two thirds of the building’s construction cost was bestowed by Nathaniel Thayer, Esq., who also donated the library’s first permanent endowment.

The library’s earliest collection was primarily comprised of volumes donated from the Library Club of Lancaster, Lancaster Agricultural Library, and several of Lancaster’s school district libraries. When opened, its collection numbered 1,200 volumes.

In 1868, Memorial Hall, commemorating Lancaster’s Civil War dead, was erected to house the growing Library. Two years later, the first expansion and renovation of the library building was completed and in 1929 a children’s room was added. In 1999 the library more than doubled its size to 19,147 square feet including an enlarged Special Collections room, two meeting spaces for large and small groups, and enough space to hold more than 70,000 volumes.

The Board of Trustees rededicated the newly renovated Library as the Thayer Memorial Library to recognize the many contributions of the Thayer Family throughout the library’s history.

The library’s historical museum was established in 1863 and houses an eclectic assortment of items representing Lancaster, including: local Civil War memorabilia, pre-historic tools, Elias Sawyer c1704 plate, 19th century locally manufactured items, documents, photographs, maps, prints, signs, pottery, tools, bottles, local church and public and private school memorabilia, local period clothing and costume samples, local 19th century physician’s instruments, native-born Luther Burbank memorabilia, furniture, Lancaster Elm memorabilia, and miscellaneous artifacts from the Lancaster Town Poor Farm.