Sumner Lake State Park lies in eastern New Mexico along the Pecos River, about eight miles northwest of Fort Sumner. Its central feature is Sumner Lake, a 4,500-acre reservoir created in 1939 when the United States Bureau of Reclamation built Sumner Dam across the river. The lake is known for fishing, including largemouth bass, catfish, crappie, and walleye. Beyond the reservoir, the park protects a plains-and-desert environment where one-seed juniper, honey mesquite, and spiny cholla are common. It is also important for wildlife, including the Sandia hairstreak, New Mexico's state butterfly, and about 50 other identified butterfly species.