The Tresoar is the central holding institution of books and archives of the province of Friesland, situated in the north of the Netherlands. The province of Friesland has its own cultural identity, shaped especially by the Frisian language, which is spoken alongside Dutch by the people of Friesland. The Tresoar is also a historical and literary centre, not only as a repository of print and archives, but also as a centre for cultural activities related to the historical collection. Tresoar is thus an institution which combines the functions of a library, archive and museum, all for the preservation of Frisian culture.
The library is based on a rich variety of early book collections. The inclusion of collections has always been made from the principle of gathering together aspects of the history of Friesland, interpreted as broadly as possible. The oldest parts of the collection of the Tresoar include the library of the University of Franeker (1585-1843). This was the oldest university of the Dutch Republic after the University of Leiden, founded ten years before that of Franeker. In the seventeenth century, Franeker was a modest town, but her university garnered an international reputation. The Franeker University Library was ultimately composed of around 10,000 volumes. Another sixteenth-century library now housed in the Tresoar is that of the Court of Friesland. The Court was the highest judicial institution in the province and existed until 1811. For the administration of justice, the Court assembled many reference works, and not exclusively jurisprudential texts. A third part of the collection of Tresoar which contributes many exceptional books is the library of Joost Hiddes Halbertsma (1789-1869), a Mennonite preacher and an important philologist. Halbertsma collected as many items as he could concerning the Frisian language and culture, and is one of the early proponents of a national Frisian culture in the early nineteenth century. Alongside these three voluminous collections, the Tresoar has been able to acquire many more specialist collections featuring old and rare books. With each addition, the Tresoar has endeavoured to collect, document and unlock aspects of the history of Friesland. But occasionally the vision of the Tresoar is not restricted to Friesland alone: the Buma library includes numerous editions of classical authors in Latin and Greek, and the Fuks library concentrates on the Hebrew language and also includes many old Yiddish books.
The collection of books held by the Tresoar is available via an online catalogue supported by WorldCat. The Tresoar actively publicises its collection to a wide audience: through publications, activities and collaborative projects. The Tresoar also strives towards participation in national and international cultural digital networks.