Immanuel on the Green is one of the oldest Episcopal congregations in the United States, with roots going back to the Church of England presence in New Castle in the late seventeenth century. The current church building dates from 1703, though it has been rebuilt and enlarged since. It faces the Green directly — together with the courthouse and the old town hall, it forms the classic colonial American triangle of government, commerce, and church.
The graveyard surrounding the church is one of New Castle's most evocative spaces, with slate headstones dating back to the early eighteenth century. The inscriptions record the town's Dutch, Swedish, and English heritage. The church interior features box pews and colonial-era woodwork. Services are still held here, and the building is open to visitors during daytime hours.