Bayou Plaquemine, a distributary of the Mississippi River and an inland route through the Atchafalaya Basin, served American Indians as a navigable waterway centuries before European exploration and from the early 1700s became a commercial transport route that promoted settlement and economic prosperity throughout Louisiana via the Atchafalaya, Red, and other rivers. By the 1800s, steamboat trade had helped the town of Plaquemine grow significantly, but flooding from the Mississippi led to construction of a levee that separated the bayou from the river. As the levee caused the river’s water level to rise higher, boats needed a lift to move between the Mississippi and the lower inland bayous, and the Plaquemine Lock solved that problem by reconnecting Bayou Plaquemine to the river. Designed by Colonel George Washington Goethals and taking 14 years to build, the lock was completed in 1909 and used a unique gravity water flow system to operate the highest fresh water lock in the world at 51 feet. Because there were no lighthouses along the Mississippi to guide ships, the Plaquemine Lock House, nicknamed the “Dutch Castle on the Hill,” was built with reflective white glazed ceramic tiles to make it more visible to river traffic. After the Gulf Intracoastal Waterway was built, the lock became its northern-most terminal, carrying cargo from the Mississippi to the Atchafalaya Basin and on to Texas. Heavy use during and after World War II strained the lock, and a larger one was completed upriver at Port Allen in 1961, after which the Plaquemine Lock was decommissioned following 52 years of operation. Thirteen years later, the U.S. Army Corps of Engineers built a levee across the mouth of Bayou Plaquemine, permanently closing its access to the Mississippi, and the bayou’s water quality then suffered because of low flow capacity. In 2006, the Fresh Water Pump Project began pumping river water back into the bayou to improve conditions for commercial and recreational use, including fishing and boating, and today the Plaquemine Lock and its surrounding 14-acre area are preserved as a state historic site listed on the National Register of Historic Places.