Melvin Price Locks and Dam is a dam and two locks at river mile 200.78 on the Upper Mississippi River, about 17 miles (27 km) north of Saint Louis, Missouri. The collocated National Great Rivers Museum, at 1 Lock and Dam Way, East Alton, Illinois, explains the structure and its engineering.
Construction began in 1979, the main lock opened in 1990, and the full structure was completed in 1994. It replaced the earlier Lock and Dam No. 26, demolished in 1990, and is the first replacement structure on the Upper Mississippi River nine-foot navigation project. The main lock is 1,200 feet (370 m) long and 110 feet (34 m) wide; the auxiliary is 600 feet (180 m) long and 110 feet (34 m) wide. The main lock has a vertical lift gate and a miter gate while the aux. lock has two miter gates. The dam is 1,160 feet (350 m) long with 9 tainter gates, each 110 feet (34 m) wide by 42 feet (13 m) high.
It is named after Illinois Congressman Charles Melvin Price.