St. Vincent Archabbey Gristmill, also known as The Gristmill, is a historic grist mill located in Unity Township, Westmoreland County, Pennsylvania. The original section was built in 1854, and is a four-story, frame structure measuring 45 feet by 40 feet. A 45 feet by 45 feet addition was built in 1883. The mill operated by steam and remains in use. It was built as part of Saint Vincent Archabbey, the first Benedictine Monastery in the United States, which opened in 1846.It was added to the National Register of Historic Places in 1978.
