The German Society of Pennsylvania, located in the Northern Liberties neighborhood of Philadelphia, is the oldest German-culture organization in the United States.

The Library was founded in 1817 and throughout its history collected a wide variety of literature and periodicals to serve the reading interests of German Society members; it continues to operate as a lending library today, with a focus on fiction, biography, and children's books in German.

In 1867, under the leadership of Oswald Seidensticker, an archive was established, with the aim of documenting German-American history and culture, and that remains the primary mission of the Library today.

As a research institution, the Horner Library is also known for its pamphlet and manuscript collections related to German-American organizations and individuals, and its holdings of 19th-century popular German works that have become rare.

Many of the city's German-culture public artworks were commissioned by the organization, including the statue of Peter Muhlenberg that now stands behind the Philadelphia Museum of Art, and the monument honoring Francis Daniel Pastorius and the first German settlers, in Vernon Park, Germantown.