Lake Texoma is one of the largest man-made reservoirs in the United States, with a surface spreading over 89,000 acres (360 km²) at the confluence of the Red and Washita Rivers. It straddles the Oklahoma-Texas border and is the second most popular lake in the United States in terms of annual visitors, with over 5 million visitors a year. This is largely attributed to not only its sheer size, which allows sports such as windsurfing and sailing, but also to its proximity to the Dallas-Fort Worth region, about 1 hour to the south. Notable cities surrounding the lake in Texas are Denison (pop. 23,000), Sherman (pop. 36,000) and Gainesville (pop. 16,000). In Oklahoma, notable cities are Durant (pop. 14,000) and Ardmore (pop. 24,000).