The Central Valley is a large, flat valley that dominates the central portion of the U.S. state of California, United States. It is home to many of California's most productive agricultural efforts. The valley stretches nearly 400 miles (600 km) from north to south. Its northern half is referred to as the Sacramento Valley, and its southern half as the San Joaquin Valley. The two halves are joined by the shared delta of the Sacramento and San Joaquin Rivers, a large expanse of interconnected canals, streambeds, sloughs, marshes and peat islands.