context: According to the United States Census Bureau, the city has a total area of 874.3 square miles (2,264 km2), making Jacksonville the largest city in land area in the contiguous United States; of this, 86.66% (757.7 sq mi or 1,962 km2) is land and ; 13.34% (116.7 sq mi or 302 km2) is water. Jacksonville surrounds the town of Baldwin. Nassau County lies to the north, Baker County lies to the west, and Clay and St. Johns County lie to the south; the Atlantic Ocean lies to the east, along with the Jacksonville Beaches. The St. Johns River divides the city. The Trout River, a major tributary of the St. Johns River, is located entirely within Jacksonville.
question: What River surrounds Jacksonville?